Technical catchment area?

[Zeraszanymum]

So... our house is just inside the catchment for the 'not so good' local school. However we live on a farm so the catchment for the 'much better' school technically goes through our property and therefore our postcode
Am I living in dreamland thinking this might be a technicality I can work with to tick the 'yes to in catchment area box!

It is based on where your house is.

It is usually measured to your front door. Will depend on which side of the line your front door is on.

In our LA catchment checks are done on every address and as a Trust we have to check our applications and verify catchment and sibling details

The normal process is that each house has a tag called the seed point which roughly corresponds to the middle of the house. That will be used for all distance measurements to the school and dictate whether you are in catchment or out of catchment but it sounds likely that you are not in catchment for your preferred school .
Having said that you need to get this sorted out so that you are not giving incorrect information on your application. If you do then this could become an issue where you lose any offered place.
Whilst I have described the normal process, many school catchments are based around old boundaries, which may or may not be on either side of your house. So you need to contact the admission office and ask them to confirm in writing which school you are in catchment for, as they will have maps that show in detail the exact spot of the boundary between one catchment zone and the other. There are many anomalies around catchment zones, especially faith schools, so you do need to check.