These types of tile are usually very strong and laid in a good bed of mortar like a cement.. The durability depends a lot on what's the tile are laid on...
What's under the tile?? Is it a concrete slab or is it a regular wood frame floor... On concrete the good quarry tile is almost indestructible..On a regular wood frame floor, there can be a lot of cracked tile and bad grout joints..Especially if some heavy loads have been pushed along the floor...
You need to get down on hands and knees and look closely at all tile and joints... See how much damage there is ,,if any... These type of tile usually have wide grout joints( (about 3/8 to 1/2 inch)..So digging out any badly cracked grout is not too difficult... Most of this type of work can be done with a screwdriver and hammer ...Like using a chisel...Regrouting is not a hard job.
If the grout isn't too bad you may be able to get away with just de-greasing them and re-polishing/finishing them. The tile supply stores have a lot of products that can be used to clean, enhance, polish, and seal,, both the tile and grout. It might be worth asking at your local DIY store and i think B&Q have leaflets on how to do this type of thing
HTH
mandy