I wouldn't expect the law to change any time soon. The CAA are just starting a consultation about simplifying licencing & medical requirements but it will take a while to change the law, & that's assuming that any change will allow PMDs for ab initio training & licence issue.
Have you thought about microlights? Some of these new 3 axis ones are very capable, although 2 seat max. The BMAA website only refers to the CAA PMD but the old rules used to be a paper self declaration that you meet DVLA standards countersigned by your GP. I think those rules still apply. If you're interested, worth an eamail to the BMAA.