Tiptronic is only available on A4 Quattro's ?
Correct.
Do Audi actually produce a 1.8 A4, b6 S line Quattro with an Tiptronic box ?
I assume you mean 1.8T. Even with that one, technically I think that is a "no" as the S-Lines were only the late model 190PS's, which were manual only. They did do a 1.8T quattro sport tiptronic, but I think that was stopped by 2003 when the Sport models were furnished with the S-Line trim, even if they were still labelled as "Sports".
I only have Parkers Guide and on line car ads, such as Autotrader etc as my reference and most A4 b6's listed with Tiptronic tend to be of the bigger engine variety ?
Try searching on Sport, rather than S-Line: if it's genuinely made after 2003, then the sport models should have the S-Line body kit, even if they don't have the badges, painted brake calipers, door sills, etc.
I see Audi do produce 2.0 A4 b7, S line Quattro with Tiptronic but not a Diesel ?
Again, I assume you mean 2.0T, then yes, they do.... regarding the 2.0TDI, then I believe that there isn't that much demand for that particular combination: the people who want auto and economy (i.e. TDI) tend to go with the FWD multitronic, the people who want auto and lots of grunt for towing (TDI) AND traction (i.e. quattro) tend to go with the 3.0TDI, which is available in tiptronic.
So with the A4 B6, is safe to assume that all A4's with a Multitronic box would have had either a free of charge or subsidised gearbox replacement
Definitely not safe to assume that at all.... please note that the answers to these multitronic questions only apply to auto+FWD cars): - if it's a 2.5TDI, then it should have, but please check, do not assume. - if it's a 1.8T/1.9TDI and it failed within certain contraints, then it may have had this done previously, but I wouldn't reocommend on relying on Audi helping you out now with a 7+ year old car that has a failed multitroinic. - if it's a 2.0 / 2.4 petrol, then I'm not sure any of these were repaired/subsidised by Audi as the engines produce a lot less torque, so it should not cause a problem unless they've been seriously abused. *I believe that 5 yrs or 40k - 60k miles was the limit set by most dealers.
which can be confirmed via the service history/invoice or through Audi, I guess by quoting VIN/Reg ?
Audi should be able to confirm if you give them the VIN/reg number, preferably VIN.
Or did Audi only offer such a replacement when a gearbox fault arose, thus still quite a few A4 B6's running ok on original Multitronic boxes,
More than quite a few, since a lot of the multitronics were 2.0 NA petrols: Most NA engines still have original multitronic gearboxes. Most V6 TDI's were replaced. Not sure on the stats with the 1.8T's and 1.9TDI, but there will be a mix.
Did the free or subsidised gearbox replacement resolve the Multitronic gearbox issues ?
Yes, as far as clutch failures, that fix should make the clutch nearly as reliable as a regular auto, although I believe that they do still need more regular oil replacements than any of the other boxes (every 40k miles?).
Are the gearbox issues only associated with the multitronic box ?
The only real "known problem" with the design of B6 gearboxes was with the multitronics and their ability to cope with high torque engines.
I'm aware the paddle shift was an optional extra and although I would like that feature too, I've not come across many A4's with such a feature fitted.
It was an expensive option.
The paddle shift feature, if not already fitted is something I hope is possible to add at a later date, if feasible.
Yes*, but it's a steering wheel replacement and you'll probably either need to find a B6 wheel from a breakers (very rare) or convert over to a B7 wheel which has it's own risks or complications. I've seen a TT paddle-shift steering wheel retro-fitted to an 02 plate 1.8T cabriolet and I believe that the paddle-shift function was "live". * I'm pretty sure that this is possible, but if you're going down this route, please check with somebody like HazzyDayz (vwcruise.com) as that's the type of thing that they would be able to do, so at least they'll let you know if it's possible / how much it'll cost - note that upgrading to a B7 style wheel is NOT cheap, so might also be worth checking if you can get one from a B7/ A6 from the breakers before you commit to this path.
Is paddle shift available in both the Tiptronic and Multitronic boxes ?
Yes, pretty sure it was available on both: it's definitely available on both now.