Thanks for all the advice everyone. It is appreciated.
I understand the concerns raised regarding developing my aviation skills suitably before jumping into an aircraft like this. As such, I would be happy taking along a safety pilot for the first few long trips to become comfortable with flying the aircraft.
I have a family of 6, and whilst it would be rare for the six seats to be occupied, it would certainly allow that to happen on occasion. I also feel that it would be a more comfortable experience when there were only 3/4 pax on trips with friends or business colleagues.
As a result of this, I am conscious that I do not want to outgrow my first aircraft too quickly. I don't really fancy buying, and then trying to sell and upgrade a year or so later. So an aircraft that gives me room to develop my skills and allows me to do more when I have become a more proficient aviator would be ideal. At that time I suppose oxygen becomes more of an issue, therefore I would be happy to consider these options now.
I'm flying out of Prestwick, so plenty of runway to work with. If there were an option to rent, or share, a nice suitable aircraft in the meantime, I would be happy to do so. But I haven't so far seen anything in the area that ticks the boxes, or appears to be available.