londonbikerider wrote:20 minutes from Paddington to Moorgate during working hours? That sound very optimistic!
Euston road would be the easiest road, but it's not great.
I am not very familiar with the "Cycle Highways" or whateverthey call them, but I'd probably try to go through back roads to Regent's park, Parkway/Camden, King's X then Pentonville rd. (it's uphill, sorry!) and City Road. I'd prefer the latter to Old street, is flat but busy and narrow.
The route across Hyde Park, Pall Mall and then along Embankment Superhighway turning off north towards Moorgate after Blackfriars Bridge - may be longer but avoids any hills. Alternative via Seymour St near Marble Arch then track through near Goodge St and Barbican, probably more traffic this way but again pretty flat. Both would take 30 mins or so, the former being slightly longer.
Just one thought, if you already have a bike then why not leave it Paddington and cycle the London bit for a few weeks to see how you get on - clearly already have a way of getting to/from Maidenhead Stn. Then try the Maidenhead end even if you have to walk up the hill on way home.