Just a quick reply
a)SW-001 and 005 (Pen y Fan and Fan Fawr) and you park at the layby with burger van between them (if you are early as it fills quickly) or the bigger car park further down the road towards Merthyr
b) SW-009 and 015 (Mynydd Troed and M LLangorse) once again you park between them but parking is very limited so you need to be midweek and early again.
c) SW-008 and 013 (Cefn y Ystrad and Tor y Foel) but only if you don't mind a fairly longish walk between them if you park high up for Tory y Foel and then aim for the quarry and up to 008 .. and then back again. Alternatively, if you want some height gain then pair SW-004 and SW-013 and park in the layby between them but Tor y Foel from the dam seems a long way up when you have just been up Waun Rhydd (or it does to me!)
d) SW-006 and 007 (Fan Gyhirych and Fan Nedd) and quite a choice of parking places. We choose the long walk in along the forest track from the minor road North of the summits (park in the splay and then we both go to separate summits and then swap over!) but others park below 007 and then across the bog (preferably when dryish) and then across to 006 and back. (Sorry, I haven't a map in front of me as you have probably gathered!)
e) have a look at our log for other ideas such as Sugar Loaf and Bryn Arw (watch out for the bracken) but most others involve moving the car. I am sure the more energetic activators will come up with longer routes (such as adding SW-002 to 'b')