My ethics are somewhat different and I think my position is that the British legal system has got this one wrong. I believe your relationship should've been illegal at the time it bega - and that's because I believe the age of consent should be brought up to 18 in line with all other adult things like voting and drinking. I have the same position as Amanda, but I'd argue to go the other way.
I've long taken the position that once two adults enter a consenting relationship, it is no business of anyone else's to get involved and make moral judgments - but I do believe the line has to be drawn at legal adulthood rather than the age of consent - and the discrepancy in British law between the two should not stand.