PGA -
Stanstead handling fees are the BAA standard, and depend on whether it is high / low season. Most of the year is high season, so you will pay about £90-£100.
Handling is mandatory - this is slightly more negotiable than the landing fee - but you should expect another £90 - £100 quid to be taken from your pocket.
Then there is the slot booking (at least 4 hours before you go.....)
I recommend you call one of the handling agents listed in your Pooleys.......
On the other hand, there is some very good advice here that you can save yourself a few quid by going into one of the nearby fields. Unless of course you have a burning desire to add EGSS to your log book!