[G & M]

Do any of you use a flat surface cleaner with a vacuum attachment and if so do you recommend them. Also which is the best make?

[Delta]

Mosmatic are the best.
http://www.cleaningspot.co.uk/acatalog/300mm-Mosmatic-Flat-Surface-Cleaner---50mm-vacuum-port-MOSS300V.html?gclid=EAIaIQobChMIzMi59KvC1QIVLpPtCh1OXANyEAQYAiABEgLAoPD_BwE

What are you cleaning? If you are pressure washing garage forecourts or kitchen floors etc you could use this:
http://jetwash-uk.com/alkota-vfs-pressure-washer-water-recovery-recycling-system-single-motor/

If you are pressure washing driveways and large public areas you would need to go big:
https://www.hotandmightydirect.com/products/pressure-washer-recycling-phoenix-ta2-mv23-455

If you don't want to use a vacuum you could go with reverse extraction. This is where you use a 300? or 500 bar pressure washer to clean the surface area. The fsc has a second nozzle which blows the crud and dirty water back down the vac tube to a simple filter.
http://www.falch.com/en/applications/details/application/cleaning-outdoor.html