I assume that the response will be much like that following the introduction of microlights; nothing for a decade and then gradual regulation - the "post-911"/"7 July 2005" thing may be used to speed it up a little.
In the early 1980's I used to live in Thurrock in Essex - there was a hang-glider pilot from Tilbury who added a chainsaw motor to the front of his hang-glider and a tube to a pusher prop (remade the crankcase in glassfibre to save weight), a giant "clothes peg" throttle which he operated with his teeth. Anyway I do recall him skimming above the roof tops - may very well have been the last true unregulated flying in the UK.