[mdjlucan]

 sulphate of iron (soluble Can anyone tell me where I can get this from thank you

[New shoot]

Most garden centres will have either Westland or Vitax, which are boxes of granules, so you might have to try EBay or Amazon for that. 

Most of the stuff I found on a quick search was lawn tonic, but maybe that will do?  It might be worth looking at the lawn care section of your local gardening shop.

https://www.ebay.co.uk/itm/154536640600?hash=item23fb1a0058:g:A~cAAOSwHZ5kY6JQ&amdata=enc%3AAQAIAAAA8KKpZ4c0lkBXyZqu74j0EQBSluslhBXIVqJsiKU4PgZlS1zRa%2FU2PHrZRIViacpTA1dBum9tYrOQgEbKuq2%2FSQ5pSi2tChPscD37X7tGjyoHktyymoGQ83s08qoajC6c4LkqD%2B66T67nyP76YI4W5f6%2BEw04VD4oq72DFSUTvYrCLHMAY5hAXcGZVp44K8uZXKYFTg4Bj17KTIK04KREk81EWhtJnfCtWNXU2gqJQwz1qVFVrdx6UXW6e7y4iEYMu1zrDezQ4qLT37AazXCLYE7Vgmxpx%2F9G3jRrucwUAKPYpVVB4ANQSdm22uACqYke1Q%3D%3D%7Ctkp%3ABk9SR-aN8-iUYg

[snowdrops]

What a shame you are not a member of my gardening club,I could sell you bucket loads of the stuff, we’ll bags of 2.5kg or 25kg sacks 
Is there an allotment association or local gardening club near you that you could join if they have a trading store?

[Fisherman]

I bought 25Kg from Amazon for about £30. They also sell smaller batches. If its to treat lawn moss its best to mix it with hot water and spray it on.

[AlaninCarlisle]

I bought mine in a 25Kg sack from a local farmer-supply shop. Funny thing was when I asked for Ferrous Sulphate I got a blank stare but when I changed it to Iron Sulphate the penny dropped