Well, IMO the best control for HSM and retrofitting is the Numeryx.
Installed by many around the world, and they are based out of Dearborn Michigan.
Just across the pond from you...
http://www.numeryx.com/cnc/index.htm
This control is popular in the mold machining capital of the US for a reason.
Our cost less than 30k, installed.
In this case, money well spent as the CNC is more accurate and faster than many very expensive CNC machines at a fraction of the price. I recently met a retrofitter who installs a new Mitsubishi on his own 5 axis Kerney and Trecker CNC machines. Doing all the work themselves, their cost is 40-50k. All servos must be Mitsubishi...
No such requirments with the Numeryx, you can even mix and match AC and DC servos... You just cannot imagine the smooth servo motion until you see it for yourself.
Good Luck,