Security Alarms Domestic or Motorhome

Hello All, I've searched, but although there are plenty references on here to Motorhome Systems, particularly 'Strikeback', I was left wondering:

Anyone got any views on the suitability of a domestic alarm system, for fitting in a motorhome?

A decent (wired) unit with remote keypad, will cost me about £50 +VAT, Sensors, PIRs etc. are cheap; I'd also need external / internal sirens, probably fitted beneath somewhere (I don't fancy a domestic alarm sounder box on the side of the MH!)

Although domestic units run from 230v, they'll also use 12v from the internal backup battery when mains power is not present: adding (or substituting) a connection to the leisure battery would surely see it run for months, and it could work off mains power when on hookup.

Using a wired system will presumably use less power than the easier to fit wireless options.

Aside from integrating with the built-in immobiliser; working as an 'intruder alarm' in the conventional sense, It'd do much the same job, with contacts on doors & windows of course.

Similarly, domestic alarms also have the usual options of key fob arming, paging your mobile phone etc. but very much cheaper for the hardware; presumably through production volumes.

I'm not looking for an insurance premium reduction; since I established this only amounted to about £30. for a proper CAT1 alarm: just a good intruder alarm without paying £600. (perhaps I'll end up down that road; but at the moment I'm considering options...)

Anyone got suggestions / opinions on this?