Wedding dress alteration advice

I thought I was really lucky to find a dress I had dismissed as too expensive in a sample sale online. It was supposed to be a 10 but was more like a 14. A seamstress has most fitted the top at the same cost as the dress but it’s still too long and she’s quoted me £250 to hem it or has suggested cutting it. It’s made of parachute silk, I really don’t want to cut it but can’t spend any more money on this dress. Im thinking about hemming it myself using hemming web (as is such fine delicate material. But there’s loads of it (at least a full circle if spread out). Anyone tried this? Any tips? I don’t want to ruin it but I have to do something.