You will need to have the house cleaned and returned in a rentable condition. This will show that you have have kept it cleaned and maintained throughout your tenancy.
Sounds like the new agency isn't as pro as it should be.
If you don't get it cleaned they can take it out of the bond.
You must always complete a PCR - Property Condition Report - if the agent doesnt do them (they should as it protects the tenants,agents and landlords) do one yourself!!!
Dust on exterior windows or kitchen benchtop, brown small patches of lawn, unswept patio etc can't really be considered an issue. Reason being 'natures elements' - dry period of weather, lots of wind/seabreeze etc. There is prob a gap between tenants leaving and new ones coming in and the agent can't be liable for it. Prob moving in to new place - watering the garden etc and getting it up to a standard that you want to live in!!! The first few weeks of pain
Keep copies of receipts for your records.
Note the curtains on the PCR but don't go into finiky detail - ie speck of dirt in bath, scratch on 5th floor tile in walk in pantry. These should be classified as general wear and tear and not tenant responsibility. Now iron on carpet burn mark in carpet IS tenant - the iron doesn't just get there by magic, see what I mean in the difference?
Good luck