Point about present long-term unreliability of models in the present situation is well made, but might as have a rummage around ...
http://www.wxmaps.org/pix/temp4 A really large mass of really cold air over NW Europe in week 2 but not getting across the N Sea. All we get is the rain but (hopefully) the worst of that is being pushed south into France in week 2
Jetstream irregular but mostly weak and across Uk from NW to Wed 20th after which a string swathe all the way across the Atlantic and mostly across France - closer to S UK around Mon 25th and Fri 29th, closer to the Med at other times esp at end of Run Mon 1st/.
GFS op synoptics start with sequence of depressions moving towards and/or across UK this week until one manages to stick around and settle 970mb Sun 24th Irish Sea with cold air entrained in its circulation. That fills and then there's a repeat from the Atlantic but with the next cold LP sticking over the UK Mon 1st
GEFS apart from a couple of days around Sat 23rd, pptn is quite general. Temp profile is different in the S (cold 18th & 22nd, mild in between with all runs agreeing, then mostly around seasonal norm with poor agreement) from Scotland (consistently somewhat below norm throughout)
FCM has a less mobile pattern with LP slowing up over UK Thu 21st swinging N-wards the back S-wards with more or less cold air associated esp at first.
BBC model suggesting significant flood risk next week
War does not determine who is right, only who is left - Bertrand Russell
Chichester 12m asl