If you had a day or 2 near one of the above in England where would be the best places to visit maybe by car or with a tour guide end of April
Heathrow to visit Windsor.
How long do you want to travel? There are plenty of places with 1 to 1.5 hours drive from either airport that are worthy of a visit and even more if you want to extend the drive time.
Windsor is closest to Heathrow. Bath is probably 2.5 hours driving.
From Gatwick - the castles and gardens of Kent and Sussex, Canterbury and Rye.
Within 1.5 hours of both airports, Portsmouth (Royal Dockyard), Arundel Castle, the New Forest, Chichester and Winchester.