Damaged Windows By Olympic Bunting

During the Olympics I purchased some Olympic bunting from Sainsbury's to hang from my windows. Once the Olympics were over I took the bunting down to find that the pattern on the bunting had transferred itself on to my white window frames.

At the time I didn't think anymore about it and threw the bunting away and thought I could clean it off with some cleaning products, however this did not work. I contacted Sainsbury's customer service by email and explained the situation. The woman who I have been dealing with has actually been quite rude and condescending about the whole matter and will offer me just £30 in goodwill vouchers, however this does not get rid of the stain that is left. I was wondering where i stand with this problem. Does £30 goodwill sound enough? I have provided picture evidence to Sainsbury's to show the damage it has caused, however they are not willing to take the matter any further as they need the original product to test on.