We use the Redbus Interhouse carrier neutral facilities.
Very pleased with them - good price for the rackspace, power, execellant aircon, fm2000 fire suppression etc.

The offer an included intelligent hands service, although they've much less technically adept staff now, so a reboot is ok, but you cant get a cisco switch vlan setup :p

The racks they offer in with the rental of space are well made, Knurr, ventilated doors and roof, although we're now using custom made units deeper (1m) and different door designs, so future space will be floor footprint only.

They have multiple buildings in the UK and fibre interconnects between buildings, so we can supply services to wherever the customer wants to be located or already is.