It's well worth going for a weekend a with tads lads, Kington is a great base, such a friendly pace with a really good camp site 200 yds from the High Street.
If you do an Internet search you can find a few different accounts from people who have walked from Hay to Kington you can also buy a route map on line, just search the Offas Dyke path and select the section from Hay to Kington.
Used to do this run every year, it actually started in Hay on Wye and finished in Kington (not Knighton). It dd stop because of the foot and mouth epidemic and never started agin. Enjoyed it so much that we have been back to Kington camping and trainng over the same weekend every year since the race finished.