Sneaking driving enjoyment into family holiday (I.e. not M4)

[Matisse]

Would anyone be kind enough to let me benefit from your experience of South Wales driving route knowledge, please?

I thought it might be a commonly asked question, but a bit time with the search function didn't get me quite what I was after...

We're due to make our annual family trip from London to Pembrokeshire in the not too distant future, and this year I've got the option of using a decent car for the trip. However, sitting on the M4/A48/A40 all the way from the Severn to Saint Clears seems a waste of a good opportunity (and a V12...) given the stories I hear of great driving roads a bit further north. Are there any alternative routes anyone can suggest that would incorporate some decent driving roads without adding more than an hour or two to the overall trip (obviously I will be explaining it to the family as a short cut...)

A bit of Googling suggests Severn Bridge to Chepstow / B4235 and A472 to Usk and on via B4598 to Abergavenny / A465 to Neath, and then back onto the M4 as perhaps a decent option? Or maybe stay north a bit longer from Gilwern to Sennybridge and then back to Carmarthen on the A40?

Thanks in advance

[Jamesgt]

I live in Gilwern and work in London. I often travel up the m40 then A40 onto Cheltenham and avoid the bridge toll. This part of the journey can be sole destroying if beyond some slow traffic. Pick up the a465 near Abergavenny and all the way to Swansea?! There is a great road Chris Harris has filmed on before. B4560 from llangynidr to ebbw vale. Also the A470 from merthyr to Brecon is nice and fast. Long swooping bends with a great fast 180 near storey arms. Along that road there is the a4059 to Hirwaun. This is also a great road. Be wary of police on the a470. The other roads should be ok.

Sorry the post is a mishmash. Just about to leave work.

[zasker]

You could come off the M4 at Swindon and take the A417 to Gloucester. Then take the A40 and A4136 through the Forest of Dean to Monmouth. Then get on the A40 and stay on it to Abergavenny, Brecon and all the way down to Carmarthen.

[Matisse]

Thank you, both. With a bit of planning, maybe I can try a different "short cut" each way, as research for future trips...