Thanks for all the great responses, guys. Thought provoking stuff. I can now appreciate more why the ED30s are holding their prices so well. Sure makes it hard for prospective buyers, though!
So yesterday I purchased an MK5 GTi 3dr DSG. Collecting it tomorrow. Exact spec that I was looking for: silver, full leather interior, DSG (working flawlessly), spot-on average mileage, FVWSH, totally standard with no mods. Dealership has provided an interim service, new tyres, full valet, and 12 months MOT. Cost me just under £7k - bang-on the Parkers price. I just had to drive 120 miles oop North to get it. Worth it, though.
I simply couldn't justify another £4k for the equivalent spec ED30 at the VW dealership down the road from me. They wanted over £11k. And IMO owning an ED30 without tastefully tuning it would be a crime.
The main reason for this, is that I will be using the car as my daily driver company vehicle. But if I decide to get into modding one day, then maybe an ED30 would be worthwhile then.
Although when I probably sell this Golf GTi in 3-5 years time, it'll probably by then be worth around £5k and I'll just use it as a deposit on a second-hand Porsche.
But no doubt the MK5 ED30 is the best Golf ever made.