Now - cut it first, then scarify, and then you may need to do another quick cut to tidy it up a bit. Then aerate it and apply an Autumn Lawn treatment, such as Autumn Toplawn, together with an application of Verdone mixed up in water, which is a lawn weedkiller. If you can't get the weedkiller down in the next few days though, best left till Spring next year.
If you need to reseed some areas, you won't be able to apply any chemical treatments to those areas though.

I scarified my top lawn last weekend, the ammount of dried grass and moss that I got out of it amazed me, I did it in 2 directions...first down and then accross...it is starting to look better even now, but afterwards I felt fairly done it, it was very hard work not having a motorised scarifyer.

Right now...