mattyboy - removable tow bars are just that: completely removable and the electric flip completely out of sight: but be warned that removable tow bars will NOT accept generic tow-bar bike racks as some of them actually slot into the hole where the tow bar goes.... and as such, each tow bar manufacturer will usually only allow you to use their specific bike rack, so check the bike racks (price and functionality) as well as the tow bars...
Here's mine.... now you see it.....
now you don't! (taken approx 5 secs later - more like 10 seconds to fit it though).
The S-Line wasn't designed to work with the removable tow bar, so there is a cut-out on the bottom edge of the bumper, but as you can see, almost invisible...
Mine is the Westfalia - it's the same as the Audi OEM one (Audi just rebadge the Westfalia hardware)... it's supposed to be one one of the best on the market, but it will restrict you to the Westfalia bike rack, so make sure you're happy with that before you buy: I'm VERY happy with is as it means all the garden clear-outs, tip runs, big Ikea / Homebase trips, etc all get done with that rather than inside the car...
Here's the guys that did mine at the end of last summer (was around £400 and took a couple of hours): very good website for showing you the pro's and cons and how easilly they work once fitted, if nothing else... I got them to fit a caravan relay that allows an extra 12V feed - which gives me an extra 12V socket in the boot, so I can run a cooler box in there (or just charge my phone).
towbarexpress.co.uk