I’m considering a solar array setup on my house in southern England. Has the technology improved and commercial viability reached a tipping point where this is easy to do and is financially worth it?
A lot depends on your annual insolation. Parts of the UK are rainier than others. Suggest you survey your area - that said, changes in weather might make the UK rainier/cloudier in years to come. The tech has reached the tipping point in sunny places.
Often you can get a greater gain by sealing the house and insulating it very well. You only do it once and properly done it can last 50 years or more-. It is also very much cheaper if you do it yourself or work with a group of 10-20+ homeowners to bulk buy the raw materials.
As for sealing - think of your house as a balloon - inflate it - will it leak.
As for ventilation, use counter current heat exchange ventilators. When warm air exits it passes it's heat to cold air coming in a parallel duct with a grid of aluminium sheets transferring the heat.
In addition, in a sealed house use inductive heating for cooking(need steel/magnetic stainless cookware). It costs about the same for the energy versus gas, but fumes are eliminated.