well,
instead of putting £15 in .. for that one off job.. you should add the price of conservatory onto it too, that will cover it, but to be honest my bank statement would not be shown to the taxman in any case,
after all , when my missus bumps into me in the middle of the day for £50 for a new top, i can hardly put that down to expenses, nor can i bank it.
so its not an issue with bank statements.