They've already increased from 10 to 13 Classic sets. I'm not sure whether they plan any further increase.
I can't recall how many HST diagrams there are supposed to be from May.
Given the plan is to have 27 HST sets, I'm assuming 23-24 diagrams need covered. So 13 plus 4 is 17 (post below suggests 15 assorted HSTs), there are still somewhere between 6-9 158/170s being used on these routes which are needed elsewhere. The 2 loco hauled sets free up 4 units at rush hour, but can they get an exemption past December?
I still haven't experienced once, refurbished or otherwise, but I look forward to the increased number of sets and diagrams, and I'm sure passengers enthusiast and non-enthusiast alike will be pleased with the increase.
The post suggests that instead of increasing the diagrams during the currency of the timetable, that instead Classic sets will be swapped out for refurbished sets when available.
Therefore, there will be at least 15 refurbished sets before December out of the 26.
That's a very glass half full way to read it, I'm more inclined to believe that it means no more than 15 sets refurbished sets expected by the December timetable change.