Peugeot 307 auto gearbox failure

In 2004 I bought this car new. Within weeks the autobox was revving and clunking into gear with the sensation of a slipping clutch in between shifts. Peugeot changed auto gearbox under warranty.
In June 2017 after only 35000 miles the gearbox again started slipping. Local large reputable garage suggested Gearbox oil change and filter. All well for a few weeks. Aug 2017 gearbox slipping again . A stop and start resolved the issue for a few miles. Back to Peugeot distributer for diagnosis as recommended by Peugeot Customer Services. Peugeot diagnosed new gearbox needed £3500. Peugeot distributer says wrong oil was put in by garage who changed the oil. I asked how they new that. Answer 'because it is red and it should be brown'. Recontacted Garage who changed oil to be told that is not true, they used Dextron 3 (H) synthetic oil which they state was the correct oil. Peugeot distributer says that 'wrong oil' could well have exacerbated the problem. I understand that but 1, it is disputed that the wrong oil was used and 2. The problem existed before the oil was changed. Peugeot Customer service not interested in offering any support whatsoever despite extremely low mileage of car. I have read on net that the 'AL4' gearbox was put in Renault, Citroen and Peugeut cars and is notorious for problems. Anybody had any recompense from Peugeot for this ? It appears to me this known issue should have been subject of a recall and a proper solution especially as I had a gearbox changed under warranty when the car was new..
I have little choice but to scrap a perfectly good car other than the gearbox. any comments, solutions, would be appreciated