I could give you a couple of tips.
First of all,an experienced cab driver helps immensely.If it's possible get a cabbie with experience with this sort of thing; alot of teams and celebrities like to go to a particular hotel.If Man Utd or some other team stayed in a hotel in the area when they stayed there, chances are Chelsea will be headed there as well.
Second of all have alternate entrances covered.Top hotels stop anxious fans at the door to avoid trouble at the reception area for their other guests; usually there aren't that many bouncers in the hotel and if you can get in and act callous enough chances are they won't be able to distinguish you from the average hotel guest.
Never take half chances; if you spot Arjen Robben surrounded with bodyguards you're more likely to get a rude shove than his autograph.Don't blow it because they tend to remember lone fans well;you won't get a chance at passing off as a hotel guest if you decide to risk it early.Wait till a member of the squad is isolated or something; in a group of 28 its more than likely.
Finally don't try to keep up with the team bus too tightly if you're driving.Once I was following a celeb crew to their hotel and they veered to a highway exit two lanes away at the last minute; needless to say I ended up losing them.
Hope that helps mate
