I have owned two golfs, I keep costs to a minimum by doing any servicing myself where possible.
I have a nice garage round the corner who lets me source my own parts (luckily I get them on a discounted rate too!) but go to any motor factors locally, not halfords etc, a proper motor factors who supply garages with parts you can pick up parts pretty cheap, saves you buying them through the garage who add a markup value on them.
Usually with me I do a lot of the bits myself, fuel filter, cabin filter, air filter, brake pads i they are needed, and I take my own oil and oil filter to the garage pop them £15-£20 to change my oil and oil filter, get a stamp in the book with him ticking the oil and filter change, then I just tick the other boxes for the bits that I changed myself.
It really pays to learn how to do these tasks yourself as you can save quite a bit on labour costs, I changed my rear coil springs before.
Internet is good aswel as the official documentation on when certain things need looking at IE belt changes, water pump changes, again you can play that as you wish, source parts cheaply, find someone who will sort it for you cheaply and get it logged in service book
I never go to main dealers, ever.