LCY is closest (14 miles), but it's a pain to get there from where I am because the roads are slow in even moderate traffic, and public transport to their is poor from my direction.

(I used to live close enough to LCY that I could do wheels down to key in the front door in <30 minutes regularly. Handy when I used to fly to AMS a lot.)

LGW next (25 miles), about 40-45 mins drive depending on traffic, or just over an hour on public transport - train into VIC and GatEx.

Then LHR (28 miles), around hour driving in clear traffic (either across town, or around the M25) and as much as 2 hours in bad traffic, or allow around 1h15-1h30 on public transport.

Now, if only I could chopper over from Biggin...