Hi Dave, further to PETER01's response, I did this flight last year with BA in CW in the mini-cabin (11A) and had the following thoughts:
Outbound:
Completely full flight, I like the mini-cabin as it doesn't have the dormitory feel of the main CW cabins on 4-class birds and the crew on this sector were good. However, throughout the flight people from WTP were popping through the curtain to use the toilets in CW (a few I'm sure raided the Club Kitchen) and there were 2 kids who thought the curtain provided a fantastic hide and seek shield (although to be fair they weren't that loud). I found all of this occurred after the meal service when the main cabin lights had been dimmed and the crew weren't coming through the cabin that much. If you are in a window or the centre CW seats, you wouldn't notice people passing back and forth that much, but being in an aisle seat would be annoying I would think.
Inbound:
Not a particularly full flight in CW or WTP, so the mini-cabin felt very quiet and relaxed and without a full WTP cabin, didn't notice anybody coming through the curtain at all (was in 11K this time). The flight timings also help on the return, full daytime flight so the crew were more active in the cabin and the CSM in his hello to me actually said he'd make sure I wasn't disturbed by people coming through the curtain.
Summary:
Flight loads will make a difference, if it's a full flight people will come through the curtain, and the outbound flight times make it more likely (dark cabin and not much crew movement), so perhaps go with main cabin on the outbound and mini-cabin on the inbound sectors to experience both.

Pilot37