Rail trip plan
1. Oxford / Didcot to Paddington, or possibly Oxford to Bicester Town (via Wolvercote Tunnel), Bicester North - Marylebone
2. Paddington / Marylebone to Willesden Junction (a place that Overground maps make look like it's the centre of London)
3. Willesden Junction to Clapham Junction (Overground)
4. Clapham Junction to Wimbledon (train - £2.30, 7 minutes)
5. Wimbledon to East Croydon (tramlink, 27 minutes)
6. East Croydon to St. Pancras International ( £4.80, 30 minutes)
7. St. Pancras International to Stratford International (Javelin - £5.40 (!), 6 minutes)
8. Stratford (having walked from Stratford International) to West Ham (Tube)
9. West Ham to Barking (Tube)
10. Barking to Gospel Oak (Overground - Goblin) (40 minutes, Goblins don't go very fast)
11. Gospel Oak to Highbury and Islington (Overground)
12. Highbury and Islington to Shadwell (Overground)
13. Shadwell to Bank (DLR)
14. Bank to Waterloo (Waterloo and City)
15. Waterloo to Paddington / Marlylebone (Tube)
16. As 1 but in reverse.
(optional alternative im place of 12 and 13)
12. Highbury and Islington to New Cross (Overground)
13. New Cross to Lewisham (5 minutes, £1.80)
14. Lewisham to Bank (DLR)
It doesn't seem too mad to me.
There are some places I may stop on the way.