it depends on your main criteria - cheap, value for money or the best. there are some very good datacentres which are so expensive because they are not necessarily in the obvious locations.
questions to ask: * N+1 or N+N redundancy on power, aircon, bandwidth * how often you need access, does location matter * how secure it needs to be; some datacentres can offer Mi5 type levels of paranoia, others are simply robust * issues like flooding, fire, off flight paths, away from rivers, away from train stations (issues vibration and/or train crashes) * on-site facilities - parking, eating, secure reception of equipment, storage thereof, build/test rooms * staff helpfulness, 24x7 security and NOC? The only way to be sure is to visit a number of them and see how well they're run. The last time I did this was about five years ago and saw BSq:MK, UKS/Studley, Globalswitch2 and others. At the time UKS offered everything we wanted and we signed up for seven racks with them, never regretted it. It was a close run thing between them and BSq:MK (which wasn't quite finished at the time).
