And if leaving it sat for a year I'd be putting all new fluids and filters in it when I went to use it again -
Engine oil, transmission and diff oil, gearbox oil, brake fluid, coolant, oil filter, cabin filter, fuel filter etc - a full major service basically.
More expansive / more of a faff on some cars than others. Something like an old Mini or Defender it's something anyone with a socket set and a spare couple of hours can do. More modern cars...probably worth saving the arse ache and paying a garage £500.
Personally I wouldn't disconnect the battery and leave it dead on a new car with loads of computer systems for a year, you're asking for trouble when you come to reconnect everything. Older cars with more basic ECU's you'd probably be ok but if it were my vehicle I'd store it on trickle charge. It's what the millionaires with car collections do who might only drive one of their Ferraris once a year!