Sachakins
The most wasted of days is one without woodwork
You could ask your gas supplier to inspect it, should be no cost. Sounds too small for water or sewage. May have just been a conduit for laying cables to an old shed our outbuildings on the site.
Don't panic, just ask the relevant authorities l, starting with council as you have done. Maybe a land registry search will identify if any other outbuildings where there.
Don't panic, just ask the relevant authorities l, starting with council as you have done. Maybe a land registry search will identify if any other outbuildings where there.