Ah, if he’s going to Swansea then to Cardiff, we could send him up the Bwlch!
TJ, it’s the road that goes past Afan Argoed and is an absolute classic. The closest thing you can get to an Alpine vibe in South Wales, not because it’s steep but it’s long and winds its way through forests and villages and breaks out of the tree line to a proper pass. A4107 up from Port Talbot through Cwmafan and Cymer to the top. Big climb though!
It might be possible to take the fire road down through the wind farm from there, but not sure off the top of my head if it’s suitable for gravel tyres and a trailer. You could easily go down through Ogmore Vale though – there’s a cyclepath marked on the map, then turn left on the cyclepath to Tonyrefail. From there take the back road to Pontyclun past Llantrisant forest, duck under the M4 and go to Cardiff via St Brides, or take a longer route through Llanrithtyd, Llancafarn, Dyffryn, Wenvoe, Dinas Powys. It’s all lovely round there.