Hotel with secure/safe parking

[56Lotus]

Hi all

I'm travelling up to London to attend a classic car event at the end of June. I'm bringing my old Lotus up and need a hotel with secure or safe parking that won't break the bank. I'm looking for something in the M4, M3 corridor as I live in Devon, hopefully within the M25 as the event is in central London. I was looking a something like the Marriott Twickenham, which has parking but I'm not sure how secure it is.

Can anyone recommend anything?

Thanks

Jon Adams