@marasp, I'd be grateful for any advice on approaching publishing houses in the UK?
So, there are two things you can do in order to make some money with regards to publishing houses.
Option One: you email publishing houses directly and you tell them what you are offering, attaching your CV. You can offer editing / translation / proofreading services. Most say no, but I have had a few saying yes to translations and offering me the odd job every now and then.
Option Two: if plan number one doesn't work for you, you can make money by becoming an academic book reviewer. That's what I do, because I hit two birds with one stone and I also support my own research: I tell publishing houses that I want to review said book (I am a very experienced reviewer with over 20 book reviews related to my field of study on my CV). So, I read the books making sure that I keep them in excellent condition (no marks or anything). Then I write and publish the book reviews on academic journals. Afterwards, I have the option to sell these books on ebay or amazon. Snap! You get both fame and money! NB: Choose to review expensive books which are related to your research. Some books I have reviewed cost nearly 150 pounds and I have made good money out of them (and because they are yours, you can scan them before selling them, i.e. you keep a digital copy for your own use).