Does anyone experience similar issues?
The alarm will suddenly set off without any obvious reason, ironically it only happens during the day and not at night but when checking the car, all doors / tail are secure and windows fully closed.

Any ideas before I start spending money trying to find the reason?

Thanks Rob

It needs plugging in to diagnostics which will tell you what is triggering the alarm. 2008 G4 RRSport TDV8 current
2009 TDCi 90 current
2018 Discovery 5 HSE lux current
1994 Dakar current

I had a similar issue with my old Rover. It was the bonnet-closed sensor button failing and it drove me crazy.

For whatever reason, it would go off only at night, not during the day in the Summer. Mechanic said that daytime heating closed the sensor gap so the alarm would only go off when it cooled down.

Ahhh, Land Rovers.  2013 RRS HSE Lux, Fuji White w/Silver Pkg, 5.0 V8
Gone, but not forgotten: 1995 RR County Classic SWB, Arctic White

As above bonnet-closed sensor , common problem , it is on the left side as you look at the engine , just bypass it and see if it sorts the problem , if so then get a new sensor 2007 SUPERCHARGED HST

Thanks everyone, wil look at the sensor Rob