No personal experience Dominik but I can tell you what my friend did last winter. His was not so much cost driven but time driven. He started the TSA process last October and while waiting for the clearances he got 8 hours in on a PA-28 and more importantly he took and passed all the exams and radio practical. He flew to Florida in February and he had a 28 day window to complete. He did it in 25 days and 48 hrs.
Talking to him afterwards we tried to compare the cost between USA/UK. His course in Florida included accom, transport etc.. He negotiated a discount for the exams passed but the extra three hours and a partial re-test brought it up to the original cost and a little bit more. Also, after returning to the UK he had another 4 hours with an instructor to get the feel of UK flying again.
I cant remember the exact figures but all in all after the expenses, air fares, transfers, TSA and visa fees and bits and pieces it worked out about £280 cheaper in the USA. However, he had four weeks in the States with almost unbroken weather, continuity of training and having the exams under his belt could take a day a week off and do a bit of sightseeing.
You pays your money........
Good luck.