Hi Nicolas,
Thanks for getting back to me - I didn't set this site up in the first place and so am still learning and please forgive me, I'm not really a coder so am a bit like a fish out of water with this.
Anyway, I took another look at the payment plugin, the plugin is called eDPQ for Hikashop and the author was James L Lendrum. I didn't realise it was created by a third party developer. It has 2014 on the date - do you know if this is one of the expired developers?
Basically, I don't really understand what Barclays are asking for, and I don't know if this plugin is going to need adapting, but obviously my main concern is that the shop still keeps working after the deadline of September 14th and is as secure as it needs to be.
This feels like it's an urgent matter an I'm not really sure how to take this forwards can you help me in any way?
Regards
Duncan