Those lows to the NW often play out well for the SE quadrant of there UK – which, we must remember, contains 60%+ of the UK population. Often 'poor' sypnotics translate into decent weather on the ground for many.
There's usually a concentric pattern of rainfall to these lows, particularly if there is warm air to the South. I've noticed it often when I've been in central France: there's the central convection and frontal system over NW UK, then a dry pocket across the South East and Northern France, then a secondary cold front / trough draped across France which brings a lot of thunderstorm activity in summer and plentiful rain.
You can see this effect in the current output. Teens to early 20s mm of rain across NW Britain between now and Monday, a gap (though in the GFS 06z the gap is punctuated by a mini plume of rainfall across Kent and Essex) and 50-100mm from Benelux down through Central France to the Pyrenees.
On Saturday it looks like areas East of London could get one of those concentric rings, but that didn't show up so much in earlier runs.
Brockley, South East London 30m asl