saw the post below and though i'd ask about beaches in the east midlands, we live just outside of boston so are close to the wash etc are there any nice beaches around for us to box the horses too?.
Sandilands is just south of Sutton on Sea - I took my boy on holiday there over Easter week and we had a great time riding on the beach every day.
The council (East Lindsey I think) do have rules for riding on the beach which you can find on their website.
It's about 10 miles north of Skeggy - there are quite a few car parks which are ok for lorry or trailer parking, you may have to pay at this time of year though
Speak to East Lindsey council as I think there are restrictions during the summer. You can ride on Skegness and Mablethorpe beaches, subject to restrictions, and the stretch from Anderby Creek up away from Skegness is really gorgeous and quiet. There are also decent, quiet car parks for parking the lorry/trailer dotted along the coast between Skegness and Mablethorpe, but the lanes are really narrow. Have fun!