Two small details, both are very very very important.
1. Get a 1st Class Medical from the CAA at Gatwick, before you even consider starting, just in case. Cost £317.00
2. There are lots of fATPL holders out there with minimum hours, first time passes etc, but no chance of a job, sooooo factor in either the cost of an instructor or the dreaded Type Rating and hours. Fi about £5-7K (I think) Type Rating £20K plus £10 for 500 hours.
And it goes without saying that the prices I and eveyone else have quoted are with first time passes and minimum hours. Doable but hard.
Realisticly you are looking in the £35-40K minimum, plus the FI ot Type.
Good luck