Make regular repayments starting now unless you have a sufficiently high regular saver savings account rate to justify holding off making immediate regular mortgage prepayments and you have the discipline to use the money at the end to make a lump sum repayment.
The interest payable is directly related to the principal outstanding so as soon as you make a repayment you're reducing the interest component of all your future repayments which leads to a quicker repayment of the loan and reduction in term. Karl Jeacle's [broken link removed] is a useful tool to check the gains possible.
Assuming all your mortgage interest is below the threshold to qualify for TRS then it's a straightforward comparison of the mortgage rate versus the savings account rate. Whichever is higher, it is in principle the better strategy to make the repayments to that one. (TRS and DIRT cancel each other out in the comparison).
If not all your interest repayment qualifies for TRS then the savings account rate needs to be 1.25 times higher (because DIRT is being deducted from it) than the mortgage rate to justify paying the money into the regular saver instead of the mortgage.
Your question has been asked many times before and the more or less consensus answer as I perceive it was that, irrespective of the marginal gains that may be made from paying into a high interest savings account, it's better to pay down the mortgage for the peace of mind benefit of having a lower mortgage and more equity in your home. There's also the risk that the savings account money will end up being blown on something besides repaying the mortgage.
