Cray Valley would be interesting but the ground holds 1k.
Not had a look but they must be the lowest ranked team in the competition.
There's actually three teams left from the 8th tier, and weirdly (given that there's eight parallel leagues at that tier) they all play in the Isthmian League South East Division (which is the same league as Merstham). They're all currently in the bottom half of the table too - although I suspect that's because they've all only played three league games because of their respective cup runs, whilst many of their competitors have already played eight!
Cray Valley Paper Mills, Ramsgate and Sheppey United.
Any one of them away from home would likely be a fun day out (for the hundred or so Oxford fans who could get tickets), a TV game and safe passage into the 2nd round!