Gatwick problems might be down to crossing and poor RT discipline on a frequency which has become increasingly busy recently.
Long winded and slowly delivered first calls including every item except what the pilot had for breakfast tend to tie up the frequency for too long (particularly as someone else is sailing through the localiser!)
I've not noticed the quality of the frequency at Gatwick being an issue as much as the RT discipline and if the RT is being tied up more than necessary then there will be more crossed and blocked transmissions.