It sounds like they most certainly did check the WX at CWL. As they wouldn't have planned normal fuel uplift for a 1 hour flight and still be in the air 3 hours later.
Did it divert to BRS?
CWL suffered a fair bit of bad fog last week. Most flights still departed for CWL on time, probably with extra fuel, and if neccessary it would divert to BRS, or BHX/EXT if BRS had fog.
Pretty standard procedure for most airlines unless all alternates are also below limits, leaving no divert alternate.
Can you be clearer in what you heard?