If you feel recovered, WCD, do it. 2 other points: you won't be bothered by crowds here! Secondly, how did you get blisters after 3 miles? - something wrong there that needs to be fixed otherwise the same thing will happen again.
That's terrible, Gill, but well done for bouncing back so positively! Have you been able to defer? I would havebeen tearing my arm off in frustration . . .
One year I did both London and Halstead in the same year - did 4:30 at London and 4:16 here 3 weeks later. All depends on your fitness and, probabaly more important, the weather - hope for westerly winds and a cool breeze!
It is undulating and therefore a challenge, as TL says, but it's not hilly (2 short sharp ones early on). You have to run well within yourself and save energy if you can - it's not a course to attack!