I recommend this. I took up the offer for cycle training when I changed jobs and wanted to commute down Seven Sisters Road / Holloway Nags Head / Camden Road. It really does help.
If you want to try my route, which is basically as above then round Regent's park and down to Oxford Circus I'd be happy to ride with you, as long as you don't mind my being a bit slow and wait for me on the hills! But be aware that this route is almost all main roads. I actually prefer main roads because there are fewer turnings, but appreciate that may not be what you want.
The best place to get a route is http://www.cyclestreets.net - the site can give you a very quiet route if you want one.
The main problem then is not getting lost, while you get used to the route. The best method is to get a holder for your smart phone (e.g. from RAM), then use an app which shows you the route on a map - like cycle streets or 'bike hub' (which gives you a view like a car GPS system).
Once you get the hang of the quite routes (of which there are quite a few), it becomes a lot easier to get around.
The quite route looks to be 7 miles, 50 minutes or so, starting with Wightman road (not so nice), Finsbury park, past Arsenal, Thornill road down through Angel (this bit is all fine, with quite a few good bike crossings, west across the Tavistock road road (v full of cyclists), cavendish st, Gt Portland st - and you are at Oxford circus. It'll take a long time the first few times, then you will get faster & less often lost!
Make sure you have good brakes, ride safely (which is not the same as going in the gutter), and if you don't like a junction, get off and walk. Good tips here on the London Cycling Campaign site: http://lcc.org.uk/articles/minimising-risk-while-cycling-in-london (they are also worth joining)
This is the route I take to Soho: https://goo.gl/maps/cqAPc
It's all nice leafy back streets without much stopping or traffic, and goes through some nice areas. I avoid most main roads even as a reasonably experienced cyclist as it's just not enjoyable on the main roads. It takes a while to learn a route, I suggest trying it out on the weekend some time when you are not in a hurry.
Wouldn't mind at all "guiding" you, but I don't leave for work till quite late.
I cycle from The Salisbury on Green Lanes down to Holborn station. I've been cycling in London for just over a year, but this route for only about 3 months.
The only main roads I really use are Green Lanes and Seven Sisters Road, both of which are cycle/bus laned. I then follow Cycle Route 7, which from Finsbury Park takes you down St Thomas' Road, then past Arsenal station, up Drayton Park, across the Holloway Road (using the cycle crossing at Madras Place) then down through Barnsbury to Rosebery Avenue, which you can follow across all the way or turn down on to Holborn itself and cycle across there before going down Shaftesbury Avenue, depending on where you actually need to go.
Of course everyone is different and I do take back roads in the main, but I have no qualms with cycling on busy roads personally - all part of the fun and it helps your confidence as a cyclist (pollution argument I accept though!)
As a novice though I certainly wouldn't go over the Camden Road and down into town that way - you've got two fairly hefty climbs (for a novice) first up to Manor House and then over the ridge on Camden Road itself, which can be quite stressful if you've got buses trying to get by you.
Cycle Route 7 is really popular with cyclists and it's not uncommon to be in a proper "peloton" of 30+ riders (which has its drawbacks as much as its advantages!)
I think the best way to approach it is to recce a route when you're not under time pressure and find out which roads are best - weekends are okay for this but don't forget the traffic builds up even on the quiet roads during the week, so take that into account.
I always say to people who are thinking of cycling in London: you must feel confident. Commit to your decision, and if you're not sure about the road ahead, stop and work it out or walk across the junction.
Good luck and hopefully see you out there!
EDIT: Here's LCN Route 7
I join it at the triangle near Finsbury Park, and turn right at the junction of Amwell Street and Rosebery Avenue. That route has a few traffic lights at the bottom end, but in the main is a very quiet and pleasant cycle through leafy Barnsbury!
Agree - I was basically suggesting Route 7 + Route 0, which takes you across central London:
In my experience it's better to minimise main roads, though some are unavoidable (Green Lanes) - lorries and buses on big roads create a lot more risk. The LCN routes are generally not bad, though overcrowding is an issue in some places.