I always use "degrees" now with ALL my heading instuctions as I also have to allocate quadrantal levels on Advisory Routes.
I have yet to have an incorrect readback following this method of operation.
As for the 250 kts below FL100, as has been mentioned it has always been a requirement unless lifted by ATC.
At ScACC we are often asked if the speed limit applies by transatlantic arrivals west of Glasgow and we have to explain that out there it is mandatory and ATC cannot lift the limit.