New mortgages fell 22% last year

Presumably those figures include houses that were bought off the plans up to 18 months previously for which the mortgage was drawn down last year and the percentage drop in actual houses bought last year is much worse but are not reflected yet in the mortgage figures.
Also trading up/down would be included.

also topups and remortgages .

It fell more than I thought last year, I expected a figure not dissimilar to 2006.

Considering a significant proportion of that drop is a “delayed” figure, the actual drop is much worse.

Spreadsheet here (excel format) -

Please note:

The figures for loan size differ between the IBF data and my spreadsheet.
I include the data back to Q1 2005 the IBF report does not.