Mortgage - Changing product and house price index question

[MECHENG84]

I'll be able to change mortgage products soon, official date when our current product expires is November but we can get the ball rolling from next month. My question is do the banks estimate house prices based on the HPI quarterly or monthly. If it is quarterly would it be worth me waiting till September to start the process as the house price may have gone up again from June or will it not make much difference?

[Sarnie]

Depends which HPI they use............

[MECHENG84]

Sarnie said:

Depends which HPI they use............

Sorry to raise this one back up, can start changing product next week. It's with Leeds Building Society, Is there anyway of finding out which HPI they use? Is 1 month likely to make any difference seeing as it crosses over another 1/4?