in those circumstances you should definitely have the environmental search.
planning-wise, I think you can see any current applications on your council's website. But you also need to do some asking round about things that are in the works but not yet submitted to planning, or rejected applications. EG if Tesco have tried once and been rejected, they will try again. This kind of thing does not show up on a planning search.
chancel liability - try the vendor on this, they can only say 'don't know'!
Environmental Search; if the flats have been there for 9 years then they presumably wouldn't have been given planning permission if there were any major environmental hazards. Planning Search; see above! Chancel Repair Liability; absolutely not. Since October last year, if there is any chancel repair liability it has to be noted on the title register of the property. If it isn't (your solicitor will know), then you are not liable.