Yes, Saudi Arabia/Sunni is definitely the greater problem, even more so because they are protected from scrutiny by the UK, Europe and the US. The UK (where I was born) is literally indebted to Saudi Arabia and Qatar. I visited England in 2016. England's "dark satanic mills" have become minarets.
The UK will be majority Muslim eventually, simply because of immigration and the higher Muslim birthrate. There is a substantial number of well trained Muslim service personnel. Add nuclear weapons and stir well.......