Any recommendations for a diamond wheel tile cutter which must be capable
of
handling floor tiles.

I lost my tile cutter (since found it again in the garden shed).

I ended up cutting my floor tiles (riven slate) freehand with a 6.99
screwfix 115mm angle grinder with a diamond disc (which cost slightly more
than the grinder). It worked perfectly and was no problem getting a straight
cut if you mark the lines out before hand. Excellent for cutting difficult
bits, too. I don't know how it would work on ceramic tiles, but suspect it
might work OK.

I would also like some advice on suitable adhesives and grout for my
kitchen floor, which is now concrete as I've removed the old vinyl
tiles,

I've always used the best I could find. In my case that was Arduflex 7001 TS
(as I was laying onto wood), although there is almost certainly several more
suitable Arduflex adhesives in the range. They do grout, too.

http://www.ardex.co.uk/tileadhesives_grouts.asp

Christian.