A lot of folks find 6A and 6K to be great for couples, you are sat quite close together right at the nose.
Edit: For trivia, as it seems like you wondered why, it starts row 6 as the 747s which used to serve out of LHR (all of which are now out of service or reconfigured) had 5 rows of Upper Class seats on the top deck, so 1-5 upstairs and 6 onwards downstairs! The only 747s in use are based in LGW/MAN are of an economy-heavy leisure config.