Thanks for all the support from all of you. Sorry I couldn't get back sooner as I all hell has been breaking loose over my dissertataion!
I did sit them down on Saturday and broke it to them gently.
I started by telling them I was pregnant, it wasn't my partner of 5 years, I had fallen in love with someone else and was moving to Switzerland with them (don't ask me why Switzerland becuase I don't know)...
By the time they had stopped laughing I eventually told them what was going on, why I had chosen this route, and why I hadn't told them sooner.
They both looked really shocked, and my Mother had tears in her eyes (which she tried to hide from me). However, after the initial reaction of telling me how drastic this was, and how they were worried about how me never being able to eat 'properly' again they calmed down.
They asked all the questions I had prepared for, and even some that I hadn't and they made a point of saying how they would be there for me if I thought this was the best option.
Now I am through that I feel a lot better about what I am going to go through!