Hi Roberino. I am from the same part of the UK as you, and fly mainly from MAN. When I started my international role, my colleagues advised using AFKLM (and therefore joining FB) to avoid having to connect through LHR on a regular basis. Most of my travel is long-haul. I find AMS and CDG to be quite good for connections, with the CDG lounges in 2E usually very pleasant to use. I have no problem with T3 at MAN now that I can use the 1903 lounge. It is very quiet most of the time but elsewhere can be a drunken melee at 6am. Things may be different in a few years time when T2 is finished.
The downsides of Skyteam are:
Skyteam is also not great in India, especially with Jet Airways' demise. I am quite fortunate in usually being able arrive the day before needing to make the internal flight, so can refresh in an airport hotel (usually BLR).
MAN often means using FlyBe (the two earliest morning flights) to connect at CDG. FlyBe are awful, but may improve soon under new ownership.
FB mileage earning (and spending) are pretty poor. I find it hard to accumulate sufficient miles for anything meaningful (mix of Y, W and J travel).
There are no useful credit cards linked to FB in the UK (AFAIK).