I am a Barrister (soon to be called to the bar of England and Wales) holding an LLM degree from the UK. I am currently working in a boutique law firm.
Note that I am qualified and experienced in Copyright and IP work. Note that I undertook a whole course regarding copyrights and Intellectual Property at Law School and am well versed in the law surrounding this area. Further, note that I have advised various individuals like yourself regarding sale and purchase of copyright related material. From what you have provided, it seems what you require will be an air tight agreement for sale that ensures protection and comprehensively deals with transfer of the Copyrights. Note that I have already drafted such agreements and it will be very easy for me to do the same for you. I can further do this in a very short span of time due to my experience relating to this work.