The well-liked green PEX400 seems to be getting expensive - Screwfix
has gone from £58 to £70 just this week, and I can't find a price for
it better than about £62 (I'll probably go for £66 from the local high
street)

So is this still the best sander to get? Or should I go for an only
slightly more expensive blue Bosch GEX125? (£75) Less powerful, but I
wouldn't mind paying a bit more for a longer working life.

GEX150 (£130) or the Metabo seem significantly more expensive.