there are still some spares shops, mostly small independents, not a chain store.
unfortunately, in general I have found they only carry in stock the items they sell a lot of.
sometimes you can be lucky and they have a part that you cant get online because it is unusual and they got it in for someone who never came back.
Things like that, I tend to ask a few questions on the phone about the fault and order the likely parts before visiting site.
i.e. oven not getting hot, take replacement stat, element, fan, over temp stat.
diagnose and fix on site same day, return unused parts to espares or your preferred online store, add 30% to the cost of parts to customer.
the customer is kept happy because they get a repair in 1 day, tell all there friends that your great and had the part in stock and fixed it quickly.
most of these parts are not big money items and wont affect cashflow if it takes a few days for refund to credit you.