You've already got a lot of support from your employers so it is probable that this is what this meeting is about. There are probably internal policies and procedures that they have to follow and the apparent urgency of the meeting is likely to be about them following the policy just in case at some time you turn round to them and say they didn't help you. Phased return is a good idea and your doc can put all that on your fit note with all sorts of suggestions about how your employers can help you. Regular contact with work is an important part of making sure things in smoothly on your return and I'm sure that is what is happening here.