does the tank have scratches or any damage (as with the cabinet) ?
other wise test kits there and all the food / Nopox dosing chemicals if full are worth over £150.
RODI unit worth £70 with TDS meter (not pumped so check your water pressure)
Jacob DCT4000 is the same pump i have on my tanks and its excellent. only £50 new though.
the pump to mix salt, never heard of it but to mix salt and move water its a bonus. plus al them drums if you needed to buy would cost you over £50.
Not familiar with the light although maxspect are a very good brand !!
for £800 i think thats a fair deal. especially if you get the rock (aquaroche or whatever it is) and don't have anything yet.
if you had alot of the kit already (RO unit chemicals etc it may not be worth it. all comes down to tank condition for me :)