Don't forget it's a Bank Holiday this weekend . One alternative is to go over The Brecon Beacons via Merthyr , then Newtown and Welshpool. That's a really great drive, I've done it quite recently, takes about 30 minutes longer than going through Hereford but traffic is usually fairly light once you get past Merthyr.
Pete
Point well made Pete, Friday traffic is going to be pretty bad for a bank holiday, and to slap in some sunshine as well will potentially mean the caravans are out. At least Matt will be safe