Motor Mover Woe

Brought the van out of winter storagte today. Was planning to give it a service ready for a short trip to Cornwall.  Couldn't move it as the mover was completely dead.  It's a Purple Line EnduroEM103. I fitted it in Oct 2009. In July 2010 (bearing in mind it had stood idle all winter), the electronics failed and they replaced it free of charge under warranty. All fine until today. Went through all the checks(new battery in the remote, checked the van battery supply etc) and rang purpleline (very nice lady on phone first time, very nice man second time) who went through the reset procedure. Well nothing worked so they pronounced it 'dead'. I asked if they would repair it and they said 'No that model is obsolete'. They suggested that I purchase the latest model which is 'backwards compatible' and will replace the faulty electronic box.  As I had had such problems they offered to let me have it at cost, £100.

Now I have emailed them and suggested they might like to replace it free. They say its out of the (2 year) warranty period. I pointed out that the (second) box they sent me has only lasted 07/2010 to 03/2012 which is less than 2 years and even less if you consider that it has not been used outside of summertime (less than 2 seasons).  I said that I would consider it 'not fit for purpose under the SoG act.  Why, I asked, would I want to buy another one if they don't last longer than 2 seasons?

Question is will I get a free replacement if I offer to go to small claims court?  Am I right in thinking the replacement should also carry a 2 year warranty from the date of invoice (which I still have)?

Any advice welcome