I think you'll find that it's difficult to obtain support and parts for the Rallye from Socata (although they claim otherwise)
If you speak from personal experience, I defer to that. My experience of parts availability for the TB is very good.
But, yeah, the French will always be French, with their perfect polite manners and the "Gallic shrug" and a well polished way of disposing of issues they don't want to attend to
But hey this is aviation. Worse than double glazing and central heating
and the company with the distribution rights for TB range in the UK has gone into administration.
Air Touring have been an irrelevance for years. Which, presumably, is why they went bust
Distribution rights for the TB? There haven't been any TBs to distribute since 2002. And few people bought the TBM via them. Also see my comment below re sole agencies; you cannot have "distribution rights" in the EU. A dealer in the EU has to earn his keep with good customer service (in aviation-speak, by not sh*agging his customers).
In the early 2000s they were running a pricing scam where they would inflate prices over everybody else. This caused all half-savvy owners to buy from other European dealers, or even (covertly, for Socata tried to stop this) via U.S. contacts, from dealers in the USA. By say 2005, most people I knew were buying from one or two European dealers as a routine matter. Sole agencies had been illegal in the EU for many years and eventually Socata had to accept that.
Air Touring's only real claim to fame, apart from their historical connection, was that they were the only UK dealer able to do calibration etc on the famously unreliable KFC225 autopilot, fitted to the GT range. There is one other shop I know of, now. They had considerable expertise on the type (as one ought to expect) but IMHO the reports from customers in recent years were too variable for my liking. They had been in a more or less continuous state of open warfare with the factory in Tarbes over reimbursement of warranty claims, which resulted in the alienation of many customers. More recently, they terminated customer credit accounts (they told me so personally) due to lack of cash and I gather that eventually they were unable to get parts from Tarbes unless they paid Socata cash up front, which made getting parts rather difficult...
Apart from some people losing money in the final weeks through prepayments for work, I don't think their demise affects anybody. The likelihood of them going bust has been an open secret to all those with ears for some/many months.
Back to the topic, I think that engine will be full of corrosion and just changing the cylinders is a very bad idea. A total overhaul is a must.