Couple more comments
Airways conjestion - The airways are conjested however lets me honest, effectively preventing the private pilot from using the airways may well be a sound political expedient but I am not sure any more valid from preventing some road users using the motor way because they arent rated to do so. Moreover I suspect few private pilots will be operating above FL120 much of which may become deregulated anyway under the new European airspace proposals.
Renewals - doubtless there are a multitude of opinion on what is required to remain safe on instruments and for that matter in VMC. However surely what matters is the evidence. Consider the American model for the FAA IR and their renewal proceudure and then consider their safety record in terminal airspace at least as conjested as ours.
Moreover you can fly an approach in IMC in every terminal control zone in the UK other than Heathrow with an IMC rating - it works. and it has worked for a very long time.
Finally, and I think this the most significant point, there are many FAA PPL IRs operating in Europe. They hold a valid ICAO license that most countries accept, they fly the same aircraft as the rest of us - the only difference is they have painted an N on their aircraft. Are they less safe - I doubt it. I for one would however prefer to be regulated by our good old national authority and not by the States (as much as I like Americans!)