I may be wrong or outdated but last I knew the GNVQ Intermediate was equivelent to 4 GCSEs, a BTEC National Diploma is equivelent to 3 A Levels (BTEC National Award = 1 A Level, BTEC National Certificate = 2 A Levels).
So basically, the BTEC (provided it is a National of some type) is higher than the GNVQ level wise.