Well 7777 - we have to start with "What, exactly, do you really want?".
To
you only have to complete
http://www.caa.co.uk/docs/33/FORSRG1102.PDF for a JAA ATPL or
http://www.caa.co.uk/docs/33/FORSRG1101.PDF for a UK CAA (National) ATPL.
Whichever form you fill in, send it to the CAA at Gatwick, with a cheque for £119 and they will send you a renewal ATPL.
You don't need a flight school, you don't need an examiner, you don't need to pay
I'd be very interested to know what you have been quoted for (and how much).
So - assuming you don't want to simply renew an ATPL - what DO you want?
(Thanks, Regis).