Hi John
It's 30 years ago but I used to get across to the Brecon Beacons quite regularly when I worked in Malvern. I can remember doing two really good (but long-ish) walks as follows:-
1. Brecon along the canal to Talybont. Up through the plantations on the south east side of Talybont reservoir. Drop down to Abercynafon. Up towards Beacons main ridge via Blaen Y Glyn waterfalls to Bwlch y Ddwyallt (this bit was really off the beaten track and might make a good walk in itself). North off the main ridge along country lanes via Cantref and Cefn Cantref back to Brecon.
2. Brecon via country lanes to the ridge up to Crybin, Fan y Big and Pen y Fan and back down one of the other ridges.
You can't go to Brecon and not do some part of no. 2. The north-south ridges are spectacular!
I recall there were decent pubs in Pencelli and Talybont (both on the canal). Brecon wasn't too badly off for pubs as well.
You might also want to get across to the north west face of the Black Mountains to the east; Hay Bluff across to Twmpa and the ridges above Talgarth. You might get buzzed by gliders slope soaring from Talgarth gliding club. They can really tuck into the hillsides.
No joy on map web sites. I used 1:25000 OS maps; separate ones for the Brecon Beacons and the Black Mountains.
Have fun
Tim