previous post says it all, however without base training you can't get the type on your licence. Check how long your skills test pass remains valid.
I know Astreus do base checks and I guess someone can do it although they need to provide a TRE who will need to sign you off for training files of which he has had no input. You can surely rent the TRE and the plane somewhere but it sure as hell will cost a small fortune, even split between 3 of you. What about Ryanair ? They have to sign off all different nationality students so maybe have some experience of different training backgrounds ? It will be an -800 though.
Good luck to you and all from Sterling. An airline with a long history.