Just to expand on groundloop's correction, for the sake of tim, what Wobbles calls an ATPL is actually a 'frozen ATPL' - which is really a Commercial Pilot Licence, Instrument Rating and passes in the ATPL theory exams. This is, if you like, an airline first officer licence.
Get to 1,500 hours flying time (there are more detailed requirements about what kind of hours these are), and your ATPL 'unfreezes'to become a full Airline Transport Pilot Licence which allows you to be commander of a two-crew public transport flight; if you like, an airline captain's licence.
Otherwise wobble is correct except that it isn't always cheaper to go abroad then convert back to the UK.
cheers!
foggy.