Hey Shy,
Not fully correct now that SERA is here:
SERA.3105, Minimum heights, and SERA.5005, Visual Flight Rules, allow you to do this as a private operator so no need to inform the CAA, But SERA.3101, Negligent or reckless operation of aircraft, could catch you out if you're a single, or twin without the ability to land safely or continue the flight.
No doubt it may change in the future but that's how it stands at present.
I'll wait for the tirade of replies from those with a higher degree of wisdom along with a greater depth of knowledge and understanding that I have to exist with...
Go on then....