Just to let you know I have found a few Myrmica queens about today so they may be out now! I live in Cornwall so I guess this info might only be relevent for people in the southwest but just thought I would let you know
I managed to find a couple of Myrmica queens as well yesterday. Its a shame this species never seems to have flights aproaching the size of Lasius (flavus/niger) in my area as I can only ever find the odd Myrmica queen. Also managed to find a lone Leptothorax acevorum queen and some Formica fusca queens.