From SW website....
From September 2010, students entering a new course or progressing to a new course, who are in receipt of BTEA, will no longer be eligible for the maintenance element of the student grant.
Students in receipt of the BTEA and the maintenance grant in the 2009-10 academic year will continue to be eligible to receive both payments for the duration of their current course provided they meet the terms and conditions of both schemes.
It appears from this information that you will be okay, and will get both BTEA and Grant for the duration of your 4 year degree.