I made an enquiry with them a couple of days ago and received the following;
Dear Paul,
Thank you for your enquiry, is the spoiler an after-market product? When the car was new the struts would have had 400N in them, we can gas these struts up to 1200N depending on your requirements. We would need your old struts to remove the brackets to fit to our new struts. You will need to supply me with the Part Number which is printed on the gas struts on your car to make sure you receive the correct struts.
New struts are available at a cost of £63.81 for the pair delivered (£24.99 per strut plus £5.50 carriage and VAT), are covered by a two year guarantee and are available on next day delivery.
Some struts can be re-gassed depending on their condition so a visual inspection by us must be made in order to assess your struts, which is free of charge. If you try a re-gas and it fails within the warranty period we will discount the cost of the re-gas from new gas struts purchased from SGS Engineering. A re-gas is £35.08 delivered for the pair (£12.50 per strut plus £5.50 carriage and VAT) and struts are usually turned around within three working days. Payment can be made via credit/debit card and you will be contacted for payment once your struts have been tested.
Only issue is my struts don't seem to have a part number that I can see yet, I'll be sending them off this weekend though.