DH and I have a combined net income of about £6000 pcm (which equates to a gross income of a little over £100k per year).
We have a reasonably small mortgage by today's standards (a little under £270k) - DH's commute to London is less than an hour, but house prices are reasonable because the state schools aren't great.
We can afford private schools for DD and DS, but only by being careful with expenditure elsewhere (e.g. our house is very 'granny chic' because we can't afford to decorate, and our holiday this year was 2 weeks in a static caravan in Berwick-upon-Tweed).
DH has a similar job to the one his dad had (his mum was a SAHM). His parents managed to send him and his brother to boarding school on that salary - something we can't manage on our combined salaries. (I went to grammar school - my parents could never have afforded private).
Our current salaries are the product of years of training and planning. I worked FT when the DC were little even though I earned less than the childcare cost. All that time I was gaining experience (and making pension contributions), so the short-term loss was balanced by long-term gain.
If we'd had the same jobs 30 years ago we would have had much more spending power. I can see why people with our level of income feel 'squeezed' - and my understanding was that 'middle' refers to middle class rather than middle income.