Try contacting (write to) Chris Kelly, Air Traffic Services Manager at Liverpool John Lennon Airport, (which appears to be the closest airport to you).
I know that at this stage you just want to visit, and not necessarily a job, but first impressions are very important.
Start off by telling him that you want to be an AIR TRAFFIC CONTROLLER not OPERATOR.
It wouldn't hurt to list your achievements to date, educational qualifications/asperations and why you want to be an atco.
They're a pretty civilised bunch in ATC, and I'm sure that Chris will organise something for you if he think's you're worth it.
Liverpool train their own staff (usually ATC assistants) to become ATCO's, the majority of them being local, but please don't underestimate the competition for places, or the very hard work involved during the training.