I think we need to define what “The Army” is… It’s a big company, with very definite distinctions between the Infantry Regiments, and the Corps (RE, RAMC, REME, AAC, RLC, etc).
The Regiments are war fighters, and when they’re not fighting wars then they’ll be training for it.
The Corps are more like the RAF, in that even in the UK they’ll still have work to do, in support of overseas Ops / Exs, maintenance of equipment for the wider Service community, support to civil emergency services…
Who do you think the civvi police call when they find an bomb in a city somewhere (which happens a lot more than you’d like to think)? They’ll call in the Military.