Tom, I'm afraid you're wrong, the Gigs & Clubs scheme is only for PRS members. This from the PRS website:

You must be a member of PRS for Music to make a claim. Alternatively, if you are a member of or an affiliated performing right organisation, that organisation can use the scheme on your behalf.

If you have performed at a pub, club, bar, community centre or hotel in the previous year (based on the date of claim), submit a representative set list to us online and we'll pay the songwriters/publishers of the works performed. This includes touring performers, resident performers and DJs.

To make a claim please log into your online account and click on Report My Live Performances and then Gigs and Clubs Scheme.

PRS Gigs & Clubs scheme

It appears that "customers", ie PRS licence holders, can also have an online account, but it is not open to anyone else.

It might well be better if non-members could report their gigs as well. However the requirement to submit a representative set-list, rather than reporting actual performances, isn't really appropriate for someone who is not performing formal sets but is playing in casual sessions.

In fact it might be better if PRS made a lot more information available to non-members - for example, why can't a non-member check the PRS database to find out who owns the copyright to a particular piece of music?

One of the reasons PRS (and the Licensing Act for that matter) is out of line with the folk world is an underlying assumption that the licence holder is promoting the music, whereas the reality in the majority of cases is that they have no involvement, and no real interest, beyond providing premises.

As for the MU, one of the reasons I let my membership lapse was that I did not feel it was appropriate to belong if I could not observe its rules - in particular I was not in a position to demand MU payment rates, neither could I comply with the rule not to perform alongside non-members.