If you're just starting out and just want to see some basic information about a company's fundamentals then the London Stock Exchange website is pretty decent for UK companies. So for example if you wanted to see Tesco's fundamentals you'd go here
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www.londonstockexchange.com
If you want more detail ADVFN gives you loads of ratios and other details at a glance, again this would be Tesco's
Summary of Income Statement, Balance Sheet, Cash Flow and Valuation Measures for Tesco TSCO.
uk.advfn.com
If that's not enough and you want more information, they check out Simply Wall Street. It's a bit easier on the eye than ADVFN
Research Tesco's (LSE:TSCO) stock price, latest news & stock analysis. Find everything from its Valuation, Future Growth, Past Performance and more.
simplywall.st
Also worth checking the investor relations on the company's website. I personally don't use too much more than that for research. Plenty to get your teeth into there!
I think you're pretty limited with what you get from a balance sheet. Beyond checking it's debt and a couple of ratios I don't spend much time looking at them.