Well given the good weather and a few spare minutes I have to hand, I went out to have a look and see whether I could fit the catch can.
After looking at potential installation locations near the battery, where the OEM intake used to be, and near the carbon canister, I decided on the latter as there appeared to be just enough room. If I want to change a DRL bulb I will have to remove the catch can, but at least its not a big issue.
There is a gap between the plastic slam panel cover and the slam panel itself which enabled me to slot the catch can bracket between the two layers and then bolt it in.
There was just enough clearance between the bottom of the can and the belts on the side of the engine to make it a viable fit:
The job went pretty smoothly apart from 2 minor workarounds.
1) Taking the excess of the right angle joint threads
The right angle joints protrude beyond the inner edge of the alloy panel which connects to the head. I had to use a long hacksaw blade and a fine file to cut these down. People with the Golf have had the same issue, so it should also affect the Leon. I then used PTFE tape on the threads to ensure that were they to move about during driving they have a slightly better seal than if they had no form of sealant. I didn't have any thread sealant / loctite to hand so this will have to do for now.
2) Connecting the right hand air pipe
If you look in the picture below, you will see a thick black OEM pipe (apologies for the lack of techno speak) connecting to a silver collar (top right hand side of the photo). This pipe clips off and on by flexing an outer hoop and it dislocates the connection.
When you have fitted the BSH panel and then you fit the metal collar (the spanner required for this is enormous, possibly 23mm or over), getting the OEM pipe back on is a nightmare as there really isn't much slack on the pipe (on the S3). The collar has to go on first. Then you have to get the OEM as straight as you can before attaching it to do it successfully otherwise the O ring pinches.
You will no longer have a pipe going to the plastic manifold section, and I found the cap which blocks this off had unusual sized connection bolts. Turns out the 3 silver bolts seem to be an imperial size allan key rather than metric (possibly due to being a US kit). Think it was 1/8".
Also I only had 3 jubilee clips (use 6mm socket for the supplied clips), so I had to supplement a spare from my personal stores.
Started the car and fortunately all works, and no unexpected side effects. I have to assume there are therefore no air leaks. Idle sat solid as usual, but initial notes are that the slight hesitation is still there as usual. Whether this will ever clear remains to be seen.
I assumed the brassy coloured wing nut at the base needed to be done up, so I'd done it up tight
(turns out this is wrong, needs to be wound out - away from the catch can, many thanks to ZBOYD for this update). A bit of AutoGlym vinyl and rubber cleaner helps you get the can in and out nice and easily.
If you are doing it yourself you will need the following tools:
1/8" allan key
T25 torx bit
Small ratchet and extension bar
6mm socket
Stanley knife
PTFE tape
Long hacksaw blade
Fine edged file
23mm(?) spanner or a very large adjustable head wrench
Drill & drill bits (if you end up drilling the slam panel)
2 nuts, washers and bolts to connect the bracket to the slam panel
A spare jubilee clip (if your kit only has 3)
Some lint free cloths to clean openings
Job time: If you are skilled, less than an hour, if you are me, hour and a half (deciding on location takes the most time)
If you are fitting it yourself, be mindful of routing your pipes, and ensure nothing rubs / fouls / kinks.
Only other thing of note is RIGHT pipe to the TOP of the catch can, LEFT pipe to the side.
Any questions fire away!