You could send an email to FIMER, and ask for the resellers in UK.
Otherwise, you might be able to order it on the site where I purchased it, it’s in Italy:
ABB VSN300 WIFI LOGGER CARD – SCHEDA ESPANSIONE WI-FI INVERTER UNO E TRIO - Solar Energy Point
There is also this one, they have it in stock:
ABB/FIMER VSN300 WIFI LOGGER CARD (tecno-logistica.it)