'm a computer science student in the UK and I've just finished my first year. I know next year I will be doing a lot more programming but there is very little C in the curriculum. I know some of my lecturers are avid C programmers would it be inappropriate to ask one of them to mentor me as I really want to be a competent C programmer or has anyone ever heard of less experienced students assisting with university research with their volunteered time?
It sounds to me like what you are looking for is less of a mentor and more of a tutor, who can work with you on basic skills and basic questions. A mentor is more a person who you talk with infrequently to get advice.
As such, asking one of your lecturers to volunteer is likely to be inappropriate. You might instead look to see if one of the upper level students might be interested---but if you need extensive tutoring, you will likely need to make it worth their while, whether that is in pay or in trade of same sort.