Getting to Stansted Airport

It is but if you leave Mountfitchet by Church road is crosses over the top of the motorway, then turn right and it brings you round to the airport. Less traffic for sure.

This maybe seems a better option.

I've been told at Liverpool St before that bicycles aren't permitted on the Stansted Express, but the National Express East Anglia website here says that it's fine if they're packed.

Stansted Express (London Liverpool Street – Stansted Airport)

Only fully folded cycles and cycles that have been flat packed in preparation for air travel can be conveyed on Stansted Express services at any time.
Folding bicycles should be transported in a protective carrying case.
Free of charge.
Reservations not required.

I'm not actually going on holiday, just picking a car up at the drop-off point and then chucking the bike in the boot, so don't want to pack it up!