a tutor not too far from the Twickenham
I see you have posted this under the 11Plus Tutors forum. So you are in the right place. For all the Surrey news (including Tiffin schools) visit the Surrey (LB Sutton & LB Kingston) forum under the 11PLUS REGIONS.
some past exam papers, do you know where can I get hold of them?
You will not find any past question papers for the Tiffin schools. The exams for the Tiffin schools comprised of Non-verbal Reasoning and Verbal Reasoning papers based on the NFER (also known as Granada Learning) question model.
You will be able to find a number of NVR and VR practice papers available in book stores as well as from this site.