Confusion with Mortgage Rate.

Barebear

We moved into the house in July '05 and went onto the discounted rate of 4.49%. We borrowed £68,000 plus fees. I had some difficulty in making payments and although I'm now up to date, I have been informed that the account will run as follows:


Letter details:

SUMMARY OF THE FUTURE PAYMENTS

Date of Effect: 1 Nov 06
Monthly Payment: £259.05

Date of Effect: 1 Dec 06
Monthly Payment: £260.40

Date of Effect: 1 Oct 07
Monthly Payment: £387.52


INTEREST RATES

Your account is on the following products:

Date of Effect: 1 Nov 06
Product code: FRA877
Product Type: Fixed
Interest Rate %: 4.49%

Date of Effect: 1 Nov 06
Product code: HVR001
Product Type: Halifax Standard Variable Rate
Interest Rate %: 6.75%

Date of Effect: 1 Dec 06
Product code: FRA877
Product Type: Fixed
Interest Rate %: 4.49%

Date of Effect: 1 Dec 06
Product code: HRV001
Product Type: Halifax Standard Variable Rate
Interest Rate %: 6.75%

Date of Effect: 1 Oct 07
Product code: HRV001
Product Type: Halifax Standard Variable Rate
Interest Rate %: 6.75%



I got this letter in October 06 and have been surprised to see that my DD payments for December and January have both been £256.43. How do I work out what my payments should be from the detail given above. It's really confusing.