Accountants ARE helpful.

you only just found out about that?

it's a 20p per mile tax-free allowance for using your own bike to get to work in fact. but you can't claim a bike as well, although if you do a reasonable mileage, it still works out better.

It's only 20p per mile for miles done during the course of your work e.g. travelling between meetings. Commuting doesn't generally count unless you are obliged by your work to travel to some particular appointment, and then I think only the extra miles count.

Edit: beaten to the button...