TransferWise has a dedicated team working on a pretty similar tool to compare fees and rates for sending money abroad. They have a lot of banks and other fintech companies: https://transferwise.com/gb/compare/
Are you just using their data and adding your affiliate link to it?
As I'm considering to move to London too, I asked two friends of friend who are Head Hunter for tech professional (web dev). What they said is: Expect 30-40k£ if you are a junior, 40-55k£ if you have some experiences.
Beside the annual salary, you can ask for good benefits: half of phone, internet, transport bills, health care, vacations.
I started mine few months ago. It's not big but by adding only 1 article each month, I come close to 10k users per months and 17k page views. My advice would be to start your own blog now, write what matters to you and do quality, not quantity.
Also, post articles on Twitter, Google+ Community pages and LinkedIn (if it's relevant to your job)
Are you just using their data and adding your affiliate link to it?