Best & easiest method to clean blue roller blinds ?

PopcornUK

Most sprays I see are for white or non-fabric blinds. I have very mould ridden (black spots) roller blinds to clean because they were in a conservatory which has a lot of condensation. I remember the owners (my parents) had this problem 6 years back and then they got them cleaned and they were spotless, I forgot to ask them how they cleaned them. They have gotten mouldy again in the last 6 years. They are away for a few days soon and I thought I would surprise them by cleaning them for when they got back. I will also get them a window Vac for Christmas so they can remove future condensation easily.

The "Curtain Magic" product I saw on Amazon looks great, and seems to be the only one I have found to do any colour on fabric, but it is a whopping £40 (inc post) for a 1 litre bottle and supposedly that won't even do all 4 blinds.

The blue roller blinds are very heavily black spotted, so I think it might take more than a quick scrub to clean them. They are fairly stiff fabric so I can't put them in the washing machine. Also due to the bad weather I am limited in ways to dry them.

Any ideas ? Any ready made sprays out there or cheaper alternatives to Curtain Magic ? Must do blue, and must do fabric. Also note, these are VERY wide and tall blinds and won't fit in the washing machine (as some might suggest the pillow case trick, can't do that with these).

Thanks !!