Hi John
I haven't been birding that long, only seriously for about three years but East Sussex isn't bad.
Joanne
Sussex is pretty good I reckon!
I'd say West Sussex perhaps has the edge.
I'm not willing to drive for hours simply because I don't drive! So I'd say I'm very much a local patch birder (having lived here since a kid) unless I go for specific birding trips abroad/Scotland/Norfolk etc.
I guess diversity of habitat is the key: - here, coastal marsh/estuary, ancient woodland, downland, farmland, meadow, wetland, heathland, all within the one County of Sussex. (Although for the non-driving city dweller, we're still talking on average an hour and a half to reach these places by public transport!) However, even 'City' has it's advantages with Black Redstart, Peregrine etc. and our urban parks/gardens often throw up passage migrants.
I'm planning to relocate in the next few years and obvious places like Norfolk may figure amongst the possible choices. However, for now, I'd say Sussex ranks pretty highly, not just in terms of diversity of species but rarities. Difficulty is, because there are so many good birding spots and it's a very large county, the coverage is probably less than it could be - Sussex birders are such awful out-of-County twitchers - usually to Kent or Devon!
'Fraid the 'half hour' rule wouldn't work for me, it can take that long for a bus to arrive to get me out of the city centre to the nearest birding patch!