And, if you really want to check out mid and south Wales, follow the A470 road south. Then travel west towards Swansea and out into the Gower peninsula to Rhosilli. You'll pass through some very fine scenery indeed - Port Talbot excepted (though, even then, the steelworks can be a stirring sight as evening falls. Just keep your windows closed and switch the air conditioning to "recirculate").

The Welsh Tourist Board does (or did) a very good guide to castles in Wales and the Marches at a very reasonable price. We toured around and found some lovely sites, for several years, on the strength of it.