Managed servers are expensive in the UK as bandwidth charges here can only be described as taking the p*** - over three or four years I've encountered soo many companies who think they can charge the earth because they've got hardware somewhere like Telehouse. It's only a building.... Look at webperf.net for a list of those who'd I'd class as the worst offenders, these people get a dedicated box that they have nothing on except the file that gets monitored, of course it's going to do well on the perf charts....
You can get a good managed dedicated box in the US for a couple of hundred quid a month with more bandwidth than the same budget will get you in the UK. If you hunt around you'll be able to find UK companies offering UK support on US boxes. It's what we're doing right now, and I mean right now! We've got our 40+ sites and about 18gb of data being imported into a new server in Texas as this is being written. Dual Xeon 2.8 with 2 x 80gb, 2gb, nightly tape backup, the works, many times more bandwidth allowance per month for three times the cost of a P3, 28gb, 1gb box in the UK. I think that backs up my statement about people in the UK taking the proverbial.....
If you're selling hosting to your clients I think you owe it to them to be hosting them on a dedicated box, otherwise you're selling something which you have no real control over, what happens if another resellers client does something to crash the box, your clients sites go down..... Some knob can easliy delete log files and crash the whole box (I've done it before by accident so it can happen) and your clients suffer from it, you get the stick and lose credibility with the people who you've worked hard to get onboard.
I've seen managed boxes from £100 a month in the US with stacks of bandwidth. I'd suggest do a compare and contrast on prices for bandwidth on both sides of the pond and don't fall for UK sales banter about how good UK b/w is. Look at the telecoms world in the States, they've had free landline calls for years and years whereas in the UK it's a pretty new thing. They're just a hell of a lot further ahead than we are.
The word virtual smacks to me as not being real. I like things that are real.
As for the control panels you're famlier with I'm sure any decent host will have them or something similar and if they don't you can ask them to sort it as part of your config, you are the client after all and if they don't play ball I'd say they don't deserve your custom.
There are pros and cons for hosting in the US, it's possible UK search results might suffer but US ones might get better and I know that I'd rather have 1% of the market over there than 10% of the market here.
It's my two cents worth but I hope this helps. Now I best bugger off n do some proper work.... 😉