Hey O_Relly,
I would say moneysupermarket, although people there wont know about immigration stuff.
I am a visa Tier 2 holder (non ILR) and I got a 90% mortgage with Halifax. We tried with Barclays too but the house got refused...apart from these 2 banks I believe all others request ILR.
Be aware that most mortgage solicitors won't know much about it either (even you paying thousands), only if you get a specialised one which is even more expensive or one that at least tries (which is a miracle).
If you have any questions, just ask the forum to see who bought in a similar situation than yours.
In my case, I had to contact HMRC directly to get the right info and read a lot the rules about overseas properties. I couldn't find this info elsewhere...most bloggers/youtubers don't bother in reading the information directly from the source (the government).
Cheers,