Chesty,
I suspect that we fly for the same company, if you search through the performance charts you will find examples which quote (as Denti states) "Maintain V2 TKOF flaps during first turn" - the example I have in front of me is runway 33 at PGF. In the main, however, it is safe to clean up and accelerate as normal in the Q400 because on one engine you will be climbing at a speed well below 190 kts anyway so there is no problem with turn radius. You will also find that if you do go to Sion/Innsbruck/Chambrey etc your simulator training for the airfield will cover any differences, as is done at the moment for Berne.
Remember that emergency turns are type specific so it is difficult to generalise - those saying to maintain V2 etc are as correct for their aircraft types (heavier/faster) as we are - your SOPs are correct.