I need to do the above trip next Sunday, arriving around lunchtime and
returning a few hours later. I have an Annual Gold Card valid Brighton -
London Terminals, and an oyster card with a PAYG balance on it.

I feel that the ideal route would be FCC to Kings Cross then Northern line
to Angel, but the Gold Card isn't valid north of Blackfriars, and there
isn't a sensible way of validating the Oyster card for travel between there
and Angel. The option of picking up the Northern Line at London Bridge
doesn't work because engineering works mean FCC aren't going that way. Is
there a paper ticket (effectively a zone 1 return) I can buy before getting
on the train at Brighton to cover the Blackfriars-Angel bit, or would I be
better off doing something else like travelling via Victoria, or taking a
bus from Blackfriars?

All ideas most welcome ...

D A Stocks