Below the high tide mark is legally crown property - I've never yet seen a ruling from HMQ that says you can't, nor ever had a complaint on the occasions when I have landed on a beach. (That said, I'm not sure I've ever seen anything saying I can either!).
A word of warning however, get the aircraft properly hosed off with clean water asap afterwards, especially the wheel/brake/undercarriage assembly.
If on the other hand it's a licenced airfield (Barra for example), or an unlicensed strip (such as Pilling sands) just follow the published local procedures as you would for any other airfield. Both of those should be in your neck of the woods and are just about big enough to land a 737 on - if you can't find anything published on Pilling, look up the local microlight clubs who use it for training (it's a great place to do a PFL!).
On the practical side, the sort of shallow ridges you get below the HT mark on a dry beach can disrupt ground effect and make your flare and landing a little abrupt, and aiming points for your landing can be hard to maintain, as can any realistic judgement of how much beach you've got left. But it is tremendous fun.
G