Post 3650 in the TP thread was LCT to KEF (rekjavik) which at the time of posting was £292. It's now £332 and can be done as a B2B in a day. For example:
https://www.google.co.uk/flights/#se...2229;sc=b;a=BA
You need to do 2, which means I think you'll have to do one mid week