Yes, I have visited that facility when it was occupied by TMA...actually spent the better part of 2/3rds of a day there with John Mulcahy, Steve Harris and Colin Harrison...excellent day, they showed me around (i.e. design facility, manufacturing facility, testing facilities,etc.), took me for lunch (on their tab), responded to all my questions, showed me products that were in development, etc.
I am sure that things have changed a tad with the new owners...also, a little mad at myself for not visiting M once there...that said, is M open to having visitors in the same way that TMA was (i.e. tell them when you will be in town and a meeting will be set) because, if so, I will go and visit the next time I am in the UK.