From a British perspective, it's quite an interesting question.
One of the anonymous people before me nailed it one the head: the class system in Britain very prevalent, but you can't say it's prevalent. There are varying levels of middle class in Britain: lower-middle class, middle-middle class (as it had been dubbed), and upper-middle class.
I've had a middle-middle class upbringing in an area that embodied the British middle-middle class very well.
Our local comprehensive schools (including my primary school) are about as good as comp schools get without being selective. We have three churches in the local area, ranging from one built in the 60s to one that dated back to the twelfth century. There are two parks about a ten-minute walk away from each other, although one is more of a play park for children and the other looks like a piece of countryside in the suburbs of a large city. The infrastructure to local grammar and private schools was very good, as well as access to the more selective comprehensives.
We didn't have too large financial struggles, as my father was (and still is) a fairly successful property entrepreneur. My sister and I go to good private schools, and the value of education was a impressed upon us from a young age. We both learnt the basics of guitar and piano, as well as basic French and Spanish (although I also learnt German for a while, and chose to continue with French and Spanish to a higher level). I live with my father in a large detached house, and my mother lives nearby in an a fairly large semi in a lovely residential where the children play out on the streets and Sunday roasts are the norm.
I have yet to graduate high school, however many people in my area have gone on to university. Reputation is a very important thing in my area, so, while most people don't ask, it's good to have your child go on to higher education, just in case.
Most people go on yearly holidays to European countries such as France or Spain, the higher end may go skiing, and the majority will go to America at least once in their life.
So, to summarise, being middle-middle class is about:

• Being able to live in relative comfort without financial stress.
• Your biggest debt being your mortgage.
• Your children having access to good schooling, and having every opportunity to improve themselves.
• Being able to go on holiday on a fairly frequent basis.
• Speaking 'proper' English, with words such as 'loo', 'sofa', 'living room', and a lack of slang terms such as 'chippy' and 'them things there', or extensive swearing.

Of course, there are negatives that come with British middle class-dom (that's not a word, but it suits):

• There's stigma about being ambitious. This applies less to the lower-middle class, who tend to be highly ambitious, but is found most especially in the middle-middle class. You have to aspire to middle-class, just like your parents, who aspired to be like their parents, who aspired to be like their parents, etc.
• Reputation means a lot. I cannot count the amount of times I was told not to talk about my turbulent-at-best relationship with my mother because "the neighbours would talk", or the times I heard my mother gossiping with friends/family at what Jenny down the street had gotten up to.
• High expectations. This kind of contradicts my point of the 'stigma of ambition', but there is a lot of pressure on middle-class students. Generally we're well equipped to deal with it (education opportunities are plentiful), but it's generally unacceptable to not go past GCSE-level education (rightfully so, in my opinion, but I'm born-and-raised middle-class), and less than ideal to not go to uni (which is a little less fair, but that's the middle class for you).

The upper- and lower-middle class a little more different. As I said earlier, the lower-middle class tend to be highly ambitious and want to get to middle-middle class status, and the upper-middle class and a glorified version of the middle-middle class, where the expectations and house prices are even higher, and bank accounts and budgets larger.
From a political perspective, the class system in general has their political parties:
Working class: typically Labour, but recently have become more UKIP and small-c conservative.
Lower-middle class: very Tory or very Labour, depending on their ambition levels.
Middle-middle class: the marginals. If they're doing well, they'll vote Labour. If the bank account shrinks, then Conservative (the capital C is important: the Conservatives aren't very conservative at all). This is also the largest class group, so these are basically the ones that politicians try to convince; working class and upper class are generally stuck in their ways.
Upper-middle class: Same as the middle-middle class, however a bit more likely to be Conservatives.
Upper class: Tory to the core.
There is some variation within this structure, however that's generally how it goes.
Hope I helped ;)