Suntot, when I spoke to IIB they said that they could do it. However, when I submitted the forms, they wanted me to move my mortgage and to do an equity release on my PPR. I wasn't interested in this and I was pretty annoyed with them as I thought they should have mentioned this to me before I filled in the application form and got all the relevant documentation.
I contacted some UK brokers that I found on the web, and most of them said the max they could get me was 75% as I wasn't a UK resident. In the end I managed to get an 80% mortgage with a UK bank through a broker in the UK.
PM me if you want more details.