Offset Mortgage Calculator?

ptee

Hello, I've been looking for a good Offset Mortgage Calculator, the ones on lenders websites are great IF/EGG etc but they only allow you to add basic savings scenarios.

I've got savings coming in various lumps (around 3 or 4 a year) over the next 10 years, I can roughly predict how much these are going to be and I'd like to see what effect these would have if I offset them against my mortgage rather than sticking them into a savings account. I know I can't judge interest rates so I can't get a completely accurate one but I don't mind that.

My mortgage is £145,000 over 25 years.

Savings that I'm expecting are...
Jan-08 £7,000.00
Jan-09 £5,000.00
Jul-09 -£6,000.00 - Final Car Payment
Jan-10 £3,200.00
Mar-10 £3,971.00
Aug-10 £1,300.00
Jan-11 £3,400.00
Mar-11 £3,300.00
Aug-11 £1,700.00
Jan-12 £4,356.00
Mar-12 £3,300.00
Aug-12 £1,550.00
Jan-13 £5,388.00
Mar-13 £3,300.00
Aug-13 £1,550.00
Jan-14 £4,956.00
Mar-14 £3,300.00
Aug-14 £1,550.00
Jan-15 £4,956.00
Mar-15 £3,300.00
Aug-15 £1,550.00
Jan-16 £4,956.00
Mar-16 £3,300.00
Aug-16 £1,550.00
Jan-17 £4,956.00
Mar-17 £3,300.00
Aug-17 £1,550.00

I'd also be looking to add £100 a month and from 2012 around £275 a month.

Obviously, the lenders websites don't allow you to add this many options so I was wondering if anyone knew of a website or spreadsheet that will allow me to add these details?
I have come across some good spreadsheets for overpayments but these would not be a true reflection of the offset mortgage as you wouldn't have the savings at the end, am I right thinking this?

Any ideas or suggestions would be welcomed.

Thanks
Pete

silvercar

egg mortgage calculator is quite good.