I'm a long-standing member of the Campaign for Real Ale (I actually became enthusiastic about the brew in the mid-1970s after previously drinking the keg on general offer at the time), so I have form in this subject.
For newcomers to English ale, I have better start by saying that it varies hugely in flavour, strength (c.3.5-10+% ABV) and colour. Also, a lot of it is still pasteurised and filtered (as was keg) so does not qualify as "real ale". Beer competitions are divided into several separate categories accordingly. Next point to note is that real ale is best drunk from the cask, not from bottles. Most bottled ale is pasteurised and filtered so that it keeps longer: RAIB (Real Ale in a Bottle) is relatively rare because it has a short bottle life unless it is very strong.
As it happens, a couple of days ago I visited the Thornbridge Brewery in Bakewell, which brews a wide range of beers in great variety, and sells them in bottles as well as to pubs. Naturally I took a selection home with me and they are excellent. Another brewery not far away is Buxton, who again make excellent, very bitter, beer which is achieving international success. These are both "micro-breweries" (albeit fairly large ones), which have a much smaller output of beer than the big national companies so their products are harder to find even in the UK, let alone abroad.
The two beers you illustrate are long-standing products of big breweries. I haven't drunk either of them for quite a while, as I prefer to look for more interesting stuff. They are certainly worth trying, though, and you'll find them very different from Fosters.
One note of warning, they should be drunk cool but not chilled. If you drink them straight from the fridge you will get little of their flavour. Around 12-15 degrees C is about right.