IMHO if you just do it, nobody is going to stop you.
I can't realistically see that any licensed airfield would take that chance; once word got out that such-and-such airfield has PCL the CAA would jump on it pronto.
As for SMS, the PCL would still be controlled from outside the airfield boundary.
Personally I think it's all about keeping the neighbours happy, and not necessarily all about safety; PCL works perfectly well elsewhere in the world, but the last thing the CAA want is a backlash from the nimbys - think of all that paperwork they'd have to deal with! The CAA knows the neighbours will tolerate the emergency services flying at night, because they know it's for a noble reason - but GA
pleasure flights? I think not..
Just to clarify, I've used PCL in the US, and think it's great. I'd love to see it used here in the UK if only, initially, until 10pm. That way I'd get to keep up my night hours!