Best to avoid the M25 during the morning rush hour as far as possible, so I would take the A303 route, which is also much more scenic than the M4.

I used to do the journey from Horsham (near Newchapel) to Bath regularly. It is possible to avoid the M25, but very complicated, and the journey is difficult in under 3 hours - AND I knew the route well.

In all honesty I would advise you to take the first route, you will only be on the M25 for 20 minutes or so, once you get on to the M3 you are heading away from London and things will be easier.

However, the M4 is quite 'boring', whereas the second route using the A303 is quite scenic, and has the advantage that you pass Stonehenge, where you can stop for a 10 minute peek (no need to pay to go in) and then take the A344 across beautiful Salisbury Plain, then left at Shrewton on to the B390 through Chitterne on to the A36 to Bath. I usually reckon on an hour from Stonehenge to Bath, it's about 40 miles.

If you do take this route, after Chitterne keep an eye out for Imber on the right hand side, it's a village that was taken over by the Army in 1943 to train for the invasion of France: the residents were promised that they would be able to return after the war - they are still waiting !

Obviously the earlier you leave the better - if you could make it 6:30 instead of 7:30 you should be clear of the M25 by 7:30.

Ugh ! RomanCitizen... you've done it again... given away our nice quiet route to the South West ! Shame on you... the hordes will be down here again in no time ! Is there no getting away from the grockles ?

Sorry !!!