Hi Marek,
Great start to the build...fantastic air brakes!
The intake splitter plates were a boundary layer air control (if I've read the posts correctly) and we did indeed call them fences. They helped prevent the boundary layer from creeping into the intakes and disrupting airflow in the intakes themselves. There were two small outlets on the underside of the fuselage, one under each mainplane if my memory serves me correctly, where this boundary layer air was vented. Anyway, we called them boundary layer air fences. You're doing a great job with all that PE, especially in that scale! Even though I spent my whole RAF career working on them, I've never built one for fear of not being able to do the aircraft justice - its not stopped me from reading all the great Vulcan builds on here mind...like Robs and yours.