Thanks ladies, well I did what any mature independant woman would do in this situation- call her dad!!!
He took all the pipes apart and OMG there was soooooo much cr#p down there, it was blocked completely with hair (WTF)straws, a paintbrush and tonnes of set fat. We scrubbed out the S bend etc and put it all back together so its all great now!!!
DH isn't answering his phone at work so he is blissfully unaware of my plumbing apprenticeship LOL
What an interesting way to start my week off!!!
Thanks again for all the replies you ladies rock.