I have a similar back ground to no better, even when we settled down, we did so in an area that neither of us had any attachment to. The place looked nice, we could afford to buy, it was half way betweeen our families and DH could commute.
It sounds as though there are lots of positives to moving. What are the benefits to staying?
A degree of homesickness is probably usual, especially if youve always lived in the same area. You're giving up a familiar environment for an unfamiliar one, but it doesn't take long for the unfamiliar to become familiar, decreasing any feelings of homesickness. One of my favourite parts of moving is going out to find new walks/day trips or experiences with the kids.
Missing family is also normal, but there's few locations within the UK, that you can't reach with a few hours travel. It just means you plan your visits, rather than popping in for a 5 minute chat x times a week/month.
The issues you've raised arent insurmountable barriers. So, your parents and sister think you're mad, why? Is it jealousy, to do with their insecurity, or reasons why they wouldnt want to move?