Wow, Dandelionpoppy I had no idea that Clothkits still existed/had been resurrected! I used to buy from them in the '80s.
OP, it's a good skill to have - I second the local colleges recommendation.
My first quick Google showed this - any use? Under "Make and Mend (Clothing)"
http://www.trafford.ac.uk/wp-content/uploads/adult_brochure2.pdf
Also sometimes large independent fabric / sewing equipment retailers run courses or know people who do; one near me runs weekend workshops e.g. "make a pair of trousers". Can be more convenient than a college class.
Try Googling local sewing courses, you'd be amazed at what little teaching craft businesses there are, e.g. trained seamstresses working around children and teaching.
Sometimes you can find local clubs too, depends where you are - I'm in a semi-rural area and I've seen a social club for any sewer or knitter advertised in a local parish magazine; could be good as you'll get people at all levels and some will be a little ahead of you so able to help.
Clothkits though are a great place to start because you don't need to worry about patterns and cutting out.
I feel so lucky, my dad (mostly!) and my mum taught me to sew by hand and machine when I was a little girl (in the 1970s). Mum used to make a few clothes for me so it was normal then.
I am never daunted now by small mends, or alterations or buttons, and I know how a fabric will behave.
Though I don't make clothes from scratch these days, I alter about every second pair of trousers I buy to fit my fat bum. Just been making a muslin curtain for a window.
Hope my essay is useful!