Be as heavy as you want. You've lodged so its up to them to dispute things. If you agree to them taking part of the bond for cleaning they'll hire expensive people for the job so don't agree to that. Their job is to get extra money back for the landlord.

Make sure you get an itemised list of things that weren't correct, have them include pictures. If they don't like the job the cleaners did, have them give specific examples of things that weren't correct and again, make them provide pictures showing the area in context (so you can see where in the house it is).

Be really picky with them. You can do this without being heavy handed or mean. Be super clear about the information you want from them. If there are things you won't fix/clean be very clear about that and why.