For the OP, the best advice I was ever given on writing a dissertation was make it as small and easy as possible. Ideally know the answer in advance. Make sure that there is plenty of good quality accessible research for your literature study. Be really clear on where you are going to get your own data from and above all don't be ambitious. An undergraduate dissertation is primarily about demonstrating your research skills, and only secondarily about any findings you might make.
When I did my degree I chose a dissertation subject that I thought would be really interesting, and I was really pleased that my tutor thought so too (this woudl now be a big red flag for me). It was a stupidly large topic to try and bit off, and I found out far too late that all the source materials and related literature were either in Arabic or French, neither of which I can read. It was incredibly stressful and I did not do very well.
For my masters I chose something which I already knew a lot about, and where essentially I was just playing with data (lots of nice graphs) and where the research was already good. I can't say it was particularly fun, but it wasn't nearly as hard and I got a good grade. There were a few nuggets in there (the team I worked in later published a short paper in the BMJ which included some of my work) but nothing groundbreaking.
I really think you would do better to take the latter approach. Oh, and you really need to base your thinking on original research not on people who make stuff up and cherry pick like Biddulf. Unless you want to do your research on child care 'gurus'.