No, not unless sperm bank is a euphemism for cum dump, then the answer would be many times!
There won't be many men from the UK that have - any children born your sperm have the right to find out who you are once they reach 18. Most men probably don't want people getting in contact with them saying "hi - technically you're my Dad"!!
I have never donated to a sperm bank, but I have donated.
A friend of mine wanted to get pregnant but she and her gf didnt have the equipment.
So we went to her doctors office and I did a donation for them.