I'm a day behind schedule with my kitchen refit..... Gas engineers are coming on Monday to replace the boiler and I really wanted to tile my floor before then.....
Problem is I have the thin self adhesive tiles down at the moment and they are impossible to remove.... Takes 15 minutes to get one up as they splinter and chip then leave thick adhesive on the floor.....
Can I just tile over the top of them??
I'm putting down slate effect ceramic tiles... The tiles already down are only about 2mm thick so I'm not fussed about the extra height....
If I can lay over the top what do I do to prep? (Easy to understand terms please)....
Looking on google it only seems to mention laying over ceramic or porcelain tiles, not the shitty thin things I need to lay over...!!
Sorry for the frat.....
Any advice will get VUs in due course....
Help me!! 
Your floors will peel up as the adhesive is probably made to stick to wood and not a synthetic material. Any moisture will stay between the tiles and pop your floors up. 
Don't tile over them!
Just gonna have to scrap them all up. There is some adhesive 'be gone' that helps but you just need to put some elbow grease into it
Cut the floor up. Replace entire subfloor with 2 layers of 3/4". Then lay your backer board on top of thinset and tape and thinset all seems. Tile is a ridgid material and needs a ridgid surface or it'll be nothing but problems down the road.
Glue and screw the flooring. Do not nail.
I found that a reciprocating saw with a scraper attachment worked really well getting old linoleum up, which I believe is very similar to what you are removing. You definitlely shouldn't tile over that shit though!
You're going to need to tear down the house and rebuild it.
Seriously though, I've tiled over some bullshit in my life, but I probably wouldn't recommend doing it over plastic or linoleum self adhesive tiles. There is a tool you can buy that may be for removing roofing that is like a heavy duty beveled 8 inch wide blade on the end of along wood handle. Using that you can get some leverage and probably get up under those things and get them up with too much heartache. Good luck!
The floor below is concrete if this changes anything?
Keep in mind that you are likely dealing with asbestos containing VCT. The last thing you want to do is to start scraping and busting that shit up.
Mortar and screw down backer board over top. Encapsulate that shit and tile over. Done.
Mark
Ditra over the top of the old flooring then tile. It is the only correct way to do t without removing them.
If you have extra height to work with, screw backer board over the linoleum tiles that are there now. Much easier and faster than removing the crap, but will make floor a bit higher.
One thing, wear a mask if you rip it up. Depending on the age of the tile it might be asbestos.