First with the new UK EASA, you need before starting training / TR anywhere, first get approval by the UK CAA, this is a new regulation I read about recently with EASA, as a friend of mine just did a A320 rating just before the changeover.
The base check I assume also needs such approval in advance, I can only speak from own experience, my friend, we did TR together, and base training was done in Slovenia, and this was not a problem.
But from my understanding, prior approval for both TR and base training is required.