I think there's a solution to undergo a course with ASTAC at Gloucestershire, I think you will have to take the necessary subjects (UK Law, UK phraseology) and than take the exam in front of their state examiners, to get the proper documents so you can undergo a OJT training in the UK (not ICAO).
I was interested in doing this, I think it was around 3-4 weeks (a week for a subject or so) but I would speculate that it cost (or so I remember) around 6 to 7k of the English money. Don't remember if accommodation was included.
This is the private way to do it, to obtain a UK licence.
Cheers.