I would use the toll road it's a breeze and you can do the trip in 3 hours. Most of the industrial units let you park there for about £15. But the pop in parking is a good site to use and could save you some doller.

Harrow and Wealdstone is decent with free unrestricted street parking just out of the town centre and 3 stops or so to Wembley, have parked there for a few Challenge Cup Finals and when the Swans were there in May.

We did that a few years back and it worked well, this year booked someones driveway near the ground for £15 as it's more cost effective for 4 of us

Morrisons car park in Queensbury. 20 mins off M1 junc 4. two stops north of wem....ber.....leee.

Good call Dave, its actually Watford Junction station. ive amended original post. i will be changing there on saturday myself... easy peasy