I would do something different each quarter just for the fun of it, come on here each time and ask us for suggestions!
You could do an ISA one quarter, buy £500 of premium bonds the next, pay your car insurance in one lump sum if the cheque arrives in time for renewal, stick it on the mortgage, ISA again, Child Trust Funds if you're feeling generous, laser hair removal on the old armpits, half on yourself half to charity? So much fun to be had!