Good afternoon Barry,
I just completed my first year of the HNC Electrical & Electronic Engineering. I didn't do the distance course as I did day release from my employer.
But Im sure the units are the same no matter which way you take it.
Get a book called "Engineering Mathematics" by K.A Stroud. Its abit costly and feels like it weighs more than a cow, but its a very very very good book, it starts at the basics of mathematics and builds up to degree level mathematics.
Also, if you undertake the Engineering Science module of the HNC "Electrical and Electronic Principles and Technology" by John Bird is another good one.
Hope this helps fella.
Linked In - http://www.linkedin.com/in/chrissj91