Can someone explain the basics of a service to me IE

How often shall it be done, difference between interim and full, how often should you get full rather than interim

What's done at a service, cost etc

Sorry to be a pain only my cars just had a £1000 worth of damage due to contaminated fuel (warranty covered) so now in thinking the engine could do with a little TLC in the form of a service lol.

I got it about 6 months ago and done around 5k miles