14% Lead in YouGov Poll

I believe this is indicative of the national mood and this is great news coming a month before the local elections. A 14% lead in the national Yougov survey sounds very promising, particularly since this is up 3% from the last local election results.
I have spent a fruitless 5 minutes trying to find a page on Google that would give me a 'historical comparison of local elections'. I know that Labour took a good kicking at the last local election and lost 900 seats and we (Conservatives) won 500. There is overall plenty of information on the last few years, but what I really want to see is the historical picture. I remember seeing some tables (at school and probably by John Snow) that indicate the overall party share in local elections and how that fluctuates, usually against governments in the mid term. I'd really like to get ahold of that now and see where this overall 14% lead might put us, if it translates into a massive swing against Labour. i.e Would we be on course to beat Labour's worst ever local election result in the 60s.
I'm off to post a request for help and recommendations for a good site for this on Coffee Shop. It will be interesting to see what I get back. Part of my reason for writing this blog is to chart my progress in pulling together these essential and vital political statistics. It's one thing to find the correct sources, and another to then be able to pull them together and make sense of them to form a cohesive argument. Modern journalists must love the web, but what did previous generations do? I suspect a lot more time was spent in dusty libraries, both private (ie. newspaper and journal's own libraries) and public.