The up side of this is that the numbers of pilots impacted is likely to be a few 100, but if you have got an IR and spent £100k on an IFR aircraft and you get shafted by EASA you are not going to be happy, and I can see why.
It's quite a bit more than "few 100", Rod1. About 10x that. And it goes right up to turboprops, light jets, corporate ops.
And there are many more UK pilots who get the IMC Rating and fly IFR in Class G. The "sports" pilot can of course do the same but illegally while enroute, and they cannot fly instrument approaches short of declaring a Mayday first.
There are also other angles on this. I know that you and others think that GA can happily exist flying homebuilts/sports/whatever from grass strips etc, but the economic fact is that the GA infrastructure in the UK and Europe does need the training business
for a PPL which leads to commercial flying.
If flight training was restricted to sports pilots (as usual I use the term loosely but you know what I mean) the numbers would be much lower and many GA airfields would close.
As it stands, even the busiest GA airfield, with a bunch of schools, cannot make ends meet on landing fees, fuel sales, and chocolate cake sales. If you take out the "PPL leading to commercial" route, there won't be much left. Look at the condition of most of them - Elstree is a pretty good example. Property development is the only way.
Of course the grass strip operators won't be concerned about any of this - why should they be?