Really confused now as somone said to jeave the M4 at J4b onto the M25 at J16.Also although subscribed don't seem to be getting a mail letting me know I have received a reply.
You don`t have any choice. The junction of the M25 is irrelevant. You go on the M4 and it joins the M25 at J4b. There is no J4a. Junction 5 is Slough, J4 is Heathrow and J4b was added between the two when the M25 was built. Keep left and it will probably say something like Watford/The North.
I am heading for the Stevenage area. Was going to use the M4 as knew it reasonably well but have been told to use the M3 as I coming from the Portsmouth area.Thanks once again.
Dead easy then. J2 of M3. Keep left. Lots of people realise they`re in the wrong lane at the last minute and cross over. There are big overhead signs for the M25 so you can`t miss it.