I thought airships were retired after the Hindenburg incident. I'd heard they were working on helium filled ones to avert future similar disasters, but didn't realise they were in general use yet. I live in London and have never seen one.
I honestly can't tell if you're being genuine or not.
Probably the most famous example is the Goodyear blimps which is primarily a US thing but it also visits London from time to time. In the US they're primarily used for sporting events and advertising.