well say half hour each way and 20 mins per socket and say 1 hour contingency . I`d allow four hours 20 mins should cover most (hopefully) , some might round this approximation for about a half days work at whatever your rate is (some might add a bit for vehicle running costs say fuel etc or some might include a figure in the hourly rate). So I personally would given them an estimate based on that and generally stick with that. You might win a bit you might lose a bit. I`d explain that it is an estimate not a fixed price just in case they are one of those jobs that run away. if I work it out at the end and it`s in say a plus or minus 10% of estimate then I`d charge as estimate.
Yes you could say £XX per hour but I almost never do that.
Reason? whatever your hourly rate is the first thing they often reply is "I don`t earn that much!" my reply is "neither do I! it`s my charging rate not my earning rate! How much do you earn and what do you think your boss charges for that work?" when you start to explain overheads such as sick pay, holiday pay, insurance, scheme membership, yadda yadda yadda , the list goes on, then sometimes they understand, sometimes not. Less hassle to just give an estimate in the first place.
I think most of us are just trying to make an honest living, a few are tradesmen from hell.
Most customers are reasonable people but a few are customers from hell.
It works both ways
Strange enough though, you never see a TV prog named "Rogue Customers"