Sorry, but an 80x60 sensor as used in the £720 model is definitely NOT good resolution.
The pulsar thermals have sensors with 384x288 resolution and that is regarded as standard
To get anywhere near that with the FLIRs you'd have to go for the E8 with a 320 x 240 core which sells for over £3900
The E4, E5 and E8 are designed for short range temperature measurement.
They have short focal length wide angle lenses which are good for looking at electrical cabinets a few feet away to find out if something is over heating.
They would be absolutely useless for our purposes, so don't waste your money
Cheers
Bruce