Thank you all very much for the advice; Alan, your knowledge and tips are always very detailed and helpful!
I have made a note of the spark plugs and leads to buy, will add them to my basket.
The timing belt looks (from the paperwork) to have last been changed 20,000 miles ago - however, this was in 2013.
Has anyone got a link (or part number) to the correct belt to purchase? I will also change the aux belts at the same time (again, a P/N or link would be most helpful).
I've always been hesitant to do the belts myself, but if it isn't too much of a fickle job, I'll give it a go this weekend. (I shall have a search on the forum for a step-by-step guide).
With regards to the main beam issue, I can hear the stepped relay (the silver one in the engine bay) making a clunking noise. With dipped beams on, clicking the mains on works, but I can't then switch them back off again. Hence my thought that it may be the stalk - again, something I shall take a look at when time permits.