Harefield is very far inland - not sure how long it would take to get to the coast, but do you know Ruislip Lido?
More info here.
And there's a railway.
Hope this helps. It's definitely within an hour of Ruislip. I'll have a google for a map.
haha. dont worry about the high jack.
dd1 + dd2 really want to go the the beach. and i feel bad as we were meant to be going away next week upto great yarmouth but we cancelled it. dont want to go too far away from the M25 area. I know if they hadf to they would send a ambulance for DH if they knew we were on holiday, but atm dh isnt weel enough for a full week away. so was thinking a 2night break near a nice beach and with hopefully some fair rides might be enough to keep the kids happy for a while.