Rob, whilst you are doubtless correct about the training records and the lack of a visa issue it would be slightly naive to rely on the UK legal system to guarantee protection.
Back in the 90s I and a number of other pilots were ripped off by a classic snakeoil salesman. The incident ended up in the national press, Flight International were slightly embarrassed as they were carrying his adverts, the police were actively involved and pursuing the gentleman in question with a view to a fraud prosecution. All seemed on track for a successful legal conclusion, faith restored in UK law etc. Unfortunately this did not come to pass as the person in question unfortunately (a cynic might say conveniently, I couldn't possibly comment) developed a dread disease which the police were lead to believe was going to be totally debilitating in very short order; unlikely as it may sound, the police showed some compassion and decided that further punishment was unnecessary and dropped the enquiry. Imagine my surprise when I find recently that said gentleman managed to continue his aviation "career" for a further 6 years, it would appear that conmen just keep on conning.
Unless you have the cash to pursue a private prosecution, which is unlikely if you have just paid for an ATPL, you will have to rely on the police and courts and unfortunately they can be conned as effectively as anyone else.
Caveat emptor and protect yourself at all times.