Thanks for all your replies.
It makes sense it is the clutch slipping, now you have mentioned it.
In terms of using the gears, I'm talking moving up maybe 5-10 mph from a happy cruising speed when over taking someone on the motorway; and the clutch was happy for me to do that in 6th up until this week. I'm not trying to accelerate very hard or anything.
Also it slips really badly in 2nd if you do put the boot in, again something new this week...
If this is the clutch going (as the majority seem to think it is!) then I want to get it done asap to avoid it going completely during the commute or something.
So far I have been quoted £700ish by the dealer, or the AutoLusso site says £495 (but they aren't really local enough).
I was looking at AHM in Hartley Wintney but I haven't made contact to get a quote yet.
Can anyone recommend a specialist in the Hampshire area that is reasonably priced?
The car is due its annual anyway so I'll get it all done at once