One picks the websites according to one's flying.
Here's a good collection.
You will find that practically all free websites deliver data from the US-run GFS weather model, which is free (subsidised by the US taxpayer, like so much in aviation
). The UK Met Office keeps most of its data confidential because they sell it, at a hefty subscription in 4 digits plus, to commercial weather repackaging firms, and it publishes F214, F215, the MSLP charts, and little else. The UKMO MSLP charts can be found, in variously out of date / disorganised forms, on sites such as
this. Or you can get it nicely set out and up to date from
Avbrief.
I think the huge number of weather sites is largely illusory because most get the stuff from the same place (GFS) or from each other
TAFs and METARs normally come from the US NWS site, or one of its spinoffs, because each country is obliged to deliver this info under ICAO obligations.
Any recommendations for aviation related websites that are reasonable accurate at forecasting the weather 3 to 4 days ahead ?
Except as a very general forecast of what is coming, in a reasonably fast moving frontal weather situation (which is quite common in the UK), you cannot forecast 3-4 days ahead with any meaning for VFR aviation. The UKMO MSLP charts are the best general guide for what is coming but unless you are an expert (i.e. a full time forecaster and a good one too) you won't be able to work out likely cloudbases or tops from that, several days ahead.