Just to add to whats been said, I've been on BP tablets since I was 19, I'm now 52. If you have to take tablets stay off the beta blockers, I've taken calcium antagonist type tablets and ACE inhibitors. Whilst on the medication I've managed a 10k pb of 32 min, 5k pb 15 min, so need to worry about our running.
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.