Does it matter if you fly AS355 or EC135? Not really. But AS355 is old ('steam driven') tech whilst the EC135 is current (glass cockpit) tech. With an eye to the future, I would do it on the EC135.
I think i might take ME, because the helicopters offshore have it. Definitely ME, if you can.
I've seen Bond have an IR-H school, is that good? Yes. Bristow also have an IR school in Gloucester. Both are good. And if you attend either, treat the course as an extended 'pre-interview'.