Hello Bedorca,
Yes the title probably gives it away
It was submitted for the R18 category which no doubt is why the BBFC had no problems with all the hardcore stuff but the sexual violence never stood a chance as the R18 doesn't allow violence. If it had been submitted for the regular 18 with the hardcore removed it no doubt would still have been cut due to the scenes of sexual violence, although the incestuous story line would have been acceptable.
Actually this film sounds a bit like Sex Wish which we were just discussing. This film also mixes hard core with extreme sexual violence.