Halfords is useful to have if it's a Sunday and nowhere else is open and you need something urgently, but it is very expensive.
For any car stuff (parts, fluids, bulbs, tools), a motor factors will sell to you at trade price so it will be about half as much as halfords charge. Only problem is they don't tend to open on sundays! Bulbs are a particular rip-off in Halfords, e.g. £20 for a single standard bulb whereas I got a pair of very good branded ones for £13 somewhere else.
A motor factors will also be able to offer good advice, whereas I've spoken to very few halfords staff that have the breadth and depth of knowledge to advise people about car problems; it often seems to be part time sixth-form kids.
Don't be tempted to pay over the top for fitting bulbs, wiper blades etc. It's usually just a 30-second job and you can save yourself £20 by doing it yourself.
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