I honestly dont believe that cloud cover will make much difference with the amount of inbuilt ambient heat in the atmosphere, the ground and buildings.
However I take your point but when its possibly already 22c plus over night, ( talking about london here)...
QUOTE from PM
Meteo/BBC use a blend of GFS and ECM data only, Meto use there own Model's which are more up to date and UK based, As well as the above. It's been very noticeable since Meteo took over UKMO contract.
Surely their models cant be that much apart for thursday.