I have found flights from Gatwick to Stornoway via Edinburgh for half the price quoted by Roz, and Edinburgh is a much nicer city than Paris for a few days stop over.
There are plenty of mobile homes to hire in Cornwall for approx. ?500 per week (high season) for the whole family (up to six people), and because they are self catering the additional costs are minimal. You can also avoid night flights, massive car parking charges at the airport, and the cost of car hire.
This is what I did for most of my childhood holidays, visiting Southern England, Northern France and Belgium. It was not until I went to university in Edinburgh that I had visited Scotland, despite (or possibly because of) my father coming from Glasgow.
I wish that when I was a child I had the opportunity to visit Greece and South Africa rather than England and France every year. You all make it sound such a disappointment that you have so much choice of affordable holidays in Europe, Africa, and in the UK (mobile homes are a lot nicer for a family holiday than most B&Bs).
I suspect that some people are just looking for excuses to get out of England and enjoy the consistent sunshine of Greece and Spain. No worries from me, but don't pretend that there are not cheap holidays in this country, you just want something better - fair enough.