So heres a brief guide to doing this job, as you won't find much about doing it from above in the workshop guide.
Remove engine cover
Remove air box (plastic rivet into inner wing, then rubber clips underneath, 2 screws by front grill for air duct to filter assembly)
When you have the grill to air box duct out, take out the little filter that's inside it and clean it out, I found a LOT of leaves and general crap in mine.
Undo the fuel filter mounts then cable tie the filter to one of the front injector pipes to get it out the way.
Remove the filter bracket form the bulkhead, 3 very odd nuts, 8mm.
I then took the intake pipework off the turbo because it was a bit in the way and covered in crap, there's two allen bolts holding it to the turbo, undo these and then just pull it off, it's quite a tight fit as it's a rubber pipe.
Next pull the brake servo vacuum pipe out of the rubber fitting on the bulkhead, it's quite stiff but will come off.
Then you need to remove the vacuum pump off the back of the cam cover, all of the torx bolts are T30s.
This is the selection of different bits that I used:
Once the vac pump is off, put that out the way and start working through the bolts holding the cam chain cover on.
First off, go for the one that's holding the black pipe which goes back under the car somewhere, to help you want to undo the small bolt on a bracket near the turbo on this pipe.
Once you have the pipe undone, put the bolt from it separate as it's a different length to the cam chain cover ones and you don't want to mix them up.
The lower horizontal bolts are the most difficult to undo, they're a bit awkward to get to, this is where the torx allen key will come in most useful.
Once you've got the cover off carefully remove the gasket too.
Then roll up some paper towel and put it in the gap between the lower cover and the cam chain, this will be useful for when you drop the bolts later on that hold the tensioner on and stop them going down into the engine, which if you do you'll cry.
Now you need to lock the engine.
To do this you need this kit:
There are three tools from the kit you need, one is the pin that locks the cam sprocket, one locks the crank, and the other is used to turn the crank pulley.
Jack the car up, and remove the under trays, look behind the sump, between the cross member and anti roll bar, on the drivers side, you will see a bung with an allen key drive, undo it, a little oil will come out but not much, a rag can catch it.
Now you need to turn the engine to TDC, this is the tricky bit, I had the GF watching the cam sprocket and trying to insert the locking pin as I turned it over.
This is what you're aiming for
The cam locking tool can go in in one position when it's not quite TDC, then you turn it 90 degrees and it locks at TDC.
There's a more thorough guide to do this in the workshop manual.
Once you've got the engine locked, then undo the bolts holding the tensioner in place, these are damn tight, you will need to use a bit of tube or a deep socket on your torx allen key to get them undone, be very careful not to let the torx bit slip and round the bolt, if you do, you'll never get them out.
The old one is a bit tricky to get out because of where the cam locking tool is, but there's a few bits that require christmas Chinese puzzle thinking, you'll find this getting the cam chain cover off too.
Then it's time to install the new tensioner, it's a bit of a fiddle to get it in-between the chains, so take your time and get it right, don't force it, make sure you lift the chain over the ridges on the guides.
You are supposed to renew the bolts that hold the tensioner on according to the workshop manual, I didn't as I didn't realise this, for the price of a few bolts I probably would do it. You should also renew the gasket but TPS provided me the wrong one so I had to reuse the original.
To do all this I throughly cleaned up all the surfaces, which is a bit tricky on the engine, whatever you do, do NOT drop bits of the original sealant into the engine, it could block oil ways in the block and cause all sorts of damage. Very carefully use a stanley knife blade and a pair of long nose pliers to pull all the old sealant off the lower surface, then degrease it.
Clean up the cam chain cover and degrease, if you're reusing the gasket, use a very good quality sealant on the cover, I used some that I had left from building a Volvo T5 engine, they use it for sealing the block together so it's pretty good stuff, but a decent loctite instant gasket would be good too, the original sealant seemed to be a type of silicone.
Smear a very thin layer of sealant on all the surfaces, but on the lower surface you need a bead about 3mm thick, put it in the groove on the cover.
Obviously remove the cam locking tool, then install the cover and slowly start putting everything back together, as haynes would say, replacement is the reverse of removal
Don't forget to take the crank locking tool out before you try to start it, or forget to take your ratchet off the crank pulley.
Good luck