Phil, I've done MK (2008 version), Wokingham and Reading. Also did Silverstone a fair few times too.
For my money, I'd rate them as follows...
Silverstone, nice and flat, hard to run the racing line as very wide track, and always very windy. Quality at the front is surprisingly low for a 5-8,000 field. I'd have been 9th if i ran a pb last year! Whereas you'd have been 3rd!!
Reading, epic field, 2nd biggest in country, very fast at the front, internationals etc...you'd be looking top 50. Couple of hills, amazing finish in the stadium, interesting trek through the town, massive overwhelming crowd support in places, deolate last 2miles up to the stadium!
Wokingham, 3/4 motorway bridges, otherwise very flat and straight. Only 2,500 field, but attracts a quality front pack. Phil Wicks won the last 2, in about 1hr04 or so. 1hr 12 would be outside the top 10.
I did Wokingham and Reading back to back, 5 weeks apart last year. In fairness I'd put masses of work into Wokingham, and then spent a week injured off work, let alone running after, and then to be honest found Reading a bit after the lord mayor's show. However, I'm sure Wokingham should come out quicker, on equal effort.
On wind, I'd say Silverstone is impossible to race without high wind, Wokingham tends to get 1 stretch over the last 3 miles, and Reading is similar, over the last 2miles before the stadium.
Reading is clearly the most impressive of the venues to finish at! Hugely expensive though.
ps apologies, you were probably wanting extra details about races you don't know.. but i;m kinda bored, so just went typing mad 
Edited: 26/06/2012 at 20:52