I think this sums things up well. The May 18 timetable is on paper rather good, in that most of the GN and SN services have quite robust paths and operational arrangements, in terms of things like crewing and turnarounds.
Thameslink is and remains the big weakness. Slightest whiff of issues and it collapses and drags down everything else with it.
Thameslink recovery seems fairly poor too - they seem to run with delays quite a lot with no attempt to run fast or terminate short - I appreciate the locations to do that north of the river are limited.