I interview and hire developers. This is my experience of looking at (recent) graduates.
A good school is a useful indicator of how rigorous your education is - but it is only an indicator. I've spoken to people from top flight universities who couldn't explain how HTTP requests work!
A much better indicator of competence - in my opinion - is your portfolio. What open source projects have you contributed to? Which conferences have you presented at? What hackdays have you attended? Have you won any prizes? Do you have a start-up you run on the side?
That said, some employers will only take people from specific universities. The higher ranked, the better. Additionally, the quality of teaching is likely to be significantly better at Goldsmiths.
My advice is not to concern yourself so much with the absolute rank - but what you can achieve at each institution.
Best of luck!