With interest rates expected to fall in the autumn, both existing and aspiring mortgage holders are facing new bouts of number crunching.

People coming to the end of existing fixed-rate mortgage contracts are having to decide whether they should avail of historically low interest rates and lock in for another few years, or take a risk and "go variable", hoping the post-EMU climate will deliver further reductions.

Those with variable mortgages are asking themselves should they take a risk that interest rates will fall even further next year or should they lock in now.

Those about to take out a mortgage face the same questions, plus a host of others: Should they sign up for a mortgage protection policy? What length of mortgage do they want? What extras do they need?

Assessing the options is a herculean task, with borrowers having to wade through endless inter-estrate tables and brochures advertising "never to be repeated" packages from banks and building societies.

Mr Richard Eberle, of fee-based mortgage consultant, REA Mortgage Services, says that when evaluating a mortgage package, the borrower should forget about the "bells and whistles" and concentrate on the underlying value. "What you are looking for is the shortest mortgage at the cheapest price," he says.

He points to another factor which is often missed - the average life of a mortgage in the Republic is seven years.

So while mortgages are more often for 20 or 25 years, people must include in their calculations the strong possibility they will not need the full life of the mortgage. The costs associated with paying off a mortgage and taking on a new one come into play at this stage.

However, there are dangers in looking at mortgages on a strictly short-term basis. For example, almost all lenders now offer a discount on the first year of a mortgage, both fixed and variable.

When comparing fixed and variable options, one should not get distracted by the rate in the first year, but concentrate on the rate after that.

All lenders have their official credit policies and in most cases this is what the consumer gets.

But the Consumers' Association of Ireland says that in face-to-face meetings between lenders and borrowers, another set of rules apply.

For example, a person visits a branch of a building society and is offered a package, which ties them into paying back the capital sum, the interest and a life cover policy.

However, the same person can go into another branch of the same building society and end up having to pay the capital sum, the interest, a life cover policy, an indemnity bond and a mortgage protection plan.

Of course the borrower is obliged under law to simply repay the mortgage to that building society. Borrowers are entitled to go elsewhere for the life cover, the mortgage protection policy and the house insurance. So the Consumers' Association advises people to shop around - advice which is continually repeated when talking about mortgages.

The "bells and whistles" referred to by Mr Eberle are on the increase. For example, First National is offering a £150 discount on ESB products on its first-time buyers package, while other building societies offer free cookers and other household items as part of their mortgage packages.

The issue of life cover needs to be approached with caution. There are two types - a diminishing life cover and a "level" life cover. The first loses its value as the mortgage progresses and only covers the outstanding balance.

A "level" life policy retains its full value and as the outstanding balance falls, has the potential to provide a cash surplus. But it is more expensive and borrowers need to make sure they are not brow-beaten into buying the level option. Young people, with no record of illness, may feel the diminishing option is better for them.

For existing mortgage holders there are different concerns, notably how to reduce the burden? In the current favourable interest rate climate serious consideration should be given by people to paying off more of their mortgage.

For example, an £80,000 mortgage taken out for 20 years at current EBS variable rates would incur monthly repayments of around £625 a month.

However, an extra £15 a month reduces the mortgage to 19 years. An additional monthly repayment of £50 would shave three years off the term of the mortgage. By reducing the term of the mortgage from 20 years to 17 years, mortgage holders stand to save £21,000 in interest payments.

But early repayment of a fixed-rate mortgage is complicated. Borrowers will generally be penalised for early repayment of loans fixed for more than a year. The reason is simple. In order to offer the borrower a fixed-rate mortgage, the lender has to enter a long-term commitment on the money markets. So if the mortgage is repaid early, the lender is left with the underlying contract - which can only be cancelled at a loss.

To recoup this, banks and building societies charge what is known as a redemption fee. This charge is levied in addition to an administration fee. The calculation used to arrive at the correct redemption fee is complicated and involves the multiplication of several variables.

Existing mortgage holders should ask their lender what kind of redemption charges will arise if they decide to break out of an existing fixed loan. First-time buyers should get an estimate of how much it will cost them to break out of a fixed arrangement and factor this in when they are weighing up the fixed and variable options.

The method used to calculate the indemnity bond is less complicated, although some lenders like TSB do not charge an indemnity bond. Once the loan is for more than 80 per cent (or 75 per cent in some cases) of the property's value, a charge is sometimes levied. Each financial institution has different charges at this stage. For example, AIB charges £3.06p for every £100 over 80 per cent of the property's value. This only applies to loans of a 20-year duration; for loans over this, the charge is £3.315 per £100.

While items like indemnity bonds can be a costly extra, the bottom-line monthly repayment is what counts.