I've updated to 2.99 but it cannot find all programmes. For example Top Gear comes up on both name and PID search but for Robot Wars and SS-GB it finds nothing. Any suggestions please?

You probably need to refresh your cache: get_iplayer --refresh

I do that every time (I've used get_iplayer for several years).

You specifically ran that exact command and then tried again? Because once I did that I could find the missing programmes.