You could use the Arcam 550 with the $1499US Monoprice Monolith 7 amp. The Arcam would power the sides and rears, and the Monolith 7 would drive the other 7 channels. The Monoprice amp is actually built by ATI and reviews posted so far seem to be very favorable regarding the amp. Not sure what it will cost to ship outside the US though.
EDIT: Monoprice has been offering 10-20% off the amp from time to time. If you go to AVSForums people post coupons when they are available. 20% off the amp is an amazing deal considering it is built by ATI. I might consider getting one in the near future.
If you're looking to add a power amp, you might want to add the forthcoming Arcam AVR390 to your list. It's due in September at £2K and early indications are that the processor is the same as the 550 and 850. if this turns out true then you'll be able to splash out on a bigger/better power amp.
I was considering the 550 to go with my ATi 3007 7ch power amp but have decided to wait to check out the 390 and hopefully make £700 saving on the new price for the 550.
The process that you follow to perform the room correction is not too difficult. I have done it 3 times so far. I am going to run it a 4th time because I recently added dual subwoofers to my system. I found the first time I ran the process the market st difficult because I had never done it before and I did not know what to expect on the outcome. Now it takes me between 30-45 minutes to complete depending on what is going on in my house. First try to pick a time to do the process where it will be the quietest. That is essential that it is as quiet as possible. What I do next is take some blue tape and mark off the area where I am be taking the measurements. Using a tape measure, I measure out 3 feet side to side and front to back around MLP, a big square area. I put tape where the corners are. Make sure you have a tripod or boom mic stand for the microphone. I then place the tripod at each position and take measurements. It goes pretty smoothly for me now using the measured area because I just place the tripod at the corner spot and take the measurement. The hardest part is stopping the test when I am interrupted by family members because they are creating some noise that can affect the measurements. Anyhow, just follow the various posted guides on the internet and you are good to go. The software on the PC (for both Windows and Macs) has side guide instructions to help you through the process.
Once you hear the end result it really is amazing. It was for me.