MAN would be a great base for the airline. If they were to concentrate on Eastern Europe, which MAN seems to suffer from, they could really give EZY and FR competition on routes to Poland etc. With MAN behind the airline, it would give them a real push.
Birmingham seems to be a weird scenario. They do have alot of loco airlines that seem to fly across most of Europe, unlike MAN, where Eastern Europe seems to be full service airline dominant.
Why would EI open it's first base in Eastern Europe? They would be taking huge risks at entering an untapped and unproven market as their first overseas base. Personally, I don't think it would be a good idea.
My guess is going with MAN in the UK. There is a bigger market there that has been tried and tested and has future potential for Long Haul if the airline wished.
Just my views!