Completely PB potential - it's just out and back along the Promenade. The only downside is that you run around the lighthouse(?) which breaks your momentum a little bit. It is a fast course though, I did the first event with no form going in and managed a 19:43, so you should be comfortably thrashing that.
I'm looking at Reigate, but my recovery from last night's football is laughable - I've been walking hunched today and the commute to and from work wasn't impressive!
Martello Tower? Guessing as haven’t done it yet.