Stanmore has quite a bit of parking, there's a college nearly next door that has parking plus they are there at the end and even directed us back to the motorway.
We did this last time. Got to High Wycombe station, plenty of free parking that day. Got on a train straight to Wembley, It's about £13.00 return so i'm told. Could not have been easier.
Parked at Stanmore last time and got the tube to Wembley Park. Intend doing the same this time, going down pretty early so may go into central London for a few hours first.
Forgot about that. Might still risk seeing if any City fans have made it to Covent Garden or Trafalgar Square. Will check the Transport for London site re any closures because of the Marathon.