This is a bit of a complex situation. Early DSG transmissions like yours had problems, and many of them were sorted under warranty with various software updates, and sometimes with total replacement of the Mechatronics unit that is the brain that works the clutch operation and gear ratio changes. To give you a bit of background, I’m copying you the official Volkswagen statement that was issued in the USA some years back, although I don’t think that European DSG vehicles ever received the same treatment regarding rectification of faults and extended warranty. Now, you don’t say how long you have owned the car, so I don’t know whether or not any earlier rectification work on your car ever took place, although it should/would be recorded on the car’s service history, which your dealer can readily access. You could of course ask them about this, but let’s keep it simple for now.
The interval for DSG servicing is indeed 40,000 miles, but it is often written that, on a purely time basis, it should be done every four years, so your car is well overdue the change in that sense. Your dealer really should have advised you of this, knowing your small annual mileage. Anyway, Volkswagen UK advertise in writing (on the web) a DSG Service for some £179. This includes an oil change, and possibly (I don’t know why it’s only “possibly” but that’s what VW says!) an oil filter change. In addition to this, and I don’t know whether this is normally included in the standard DSG service, but knowledgeable people advise that, in the case of the kangarooing problem, as well as the DSG service, a DSG reset is also required, which re-programmes the mechatronics unit and re-learns your driving style. I imagine this is because the kangarooing will have given the mechatronics unit the impression that you are a totally manic driver, and it needs to start again from scratch and re-learn how you really drive. You should quiz your dealer about this. But I would certainly try to pin down your dealer that what they are proposing will cure the problems for sure. You don’t want this service being done at significant cost, and then them telling you that you need a new mechatronics unit at some £1,400, plus goodness knows what else in extra fitting costs. You have been very faithful to your dealer, and you should expect some gratitude and help from them in this situation, particularly as they should have advised a DSG oil service some four or five years ago.
Your car is out of warranty, however, and I would be somewhat surprised if they or SEAT UK will give you anything gratis in this situation. So possibly going to an independent DSG specialist garage is not out of order, if there should be one near to you. For instance Volks Autos in Sutton, Surrey offer a DSG oil and filter change for £139, and they, like many other good independent garages, are staffed by ex-VW/Audi/SEAT/Skoda-trained staff. So don’t be afraid to make a phone call to a VW group independent specialist in your area just to have a second opinion and get a DSG service quote.
These DSG transmissions have given quite a few problems, although less so with your six-speed version with oil-bath clutches than the later seven-speed versions, I’m glad to say, and hopefully this problem will be sorted without excessive cost. If you want to give me your geographic location, I’ll see if I can find a VW Group and DSG competent garage in your area. I hope this is of some assistance and not too pessimistic. Please keep me posted on developments, or come back to me if you have further questions.