I'm a bit of fair weather cyclist because I ride a motorbike as well, but I cycle from HOP to Camden Town on average twice a week, and this is my route:

Stillness Road, Brockley Rise (past Stillness school), Courtrai, Buckthorne, left over railway footbridge, Brockley Way and on down the east side of Peckhm Rye, Rye Lane, Surrey Canal Path, Burgess Park, Portland St/Brandon St, New Kent Road (only about 100m and on designated cycle path), local streets behind E&C, Webber Street, Waterloo Rd, Waterloo Bridge, Covent Garden, Drury Lane, British Museum, Russell Square, Gordon Street, up the west side of Euston station, Hampstead road, and then back streets up to Parkway in Camden Town.

It takes me about 45 - 50 minutes depending on how I'm feeling, a bit longer on the way back.

I'd be happy to ride with anyone who is unfamiliar with the route. I do leave a bit later than usual though, around 915am.

Cheers,
KK