I do all my service myself. I may not get the booked stamped however i will eventually have a folder full of receipts. oil/filter changes every 5K.
How i see it is that i would rather see a massive folder full of frequently changes on i.e oil/filters/fluids then a few paperwork.
It even costs me more if i do 3-4 oil changed in a year (which i assuming i will be doing so) when i could just pay £120 for the year service from my indy garage.
I know what stuff is going in my car, and IT will be done properly.
I have a few mechanics in the trade and the stories they tell me is unbelievable.
To your question, i wouldnt worry about it, keep all your receipt/ note down the mileage the changes happen.