I've had a Netaheat (and a Profile)
very advanced for their time. But not suitable for DIY repairs.
If you ask around your local independent Gas installers, you will probably find one (may be a more mature gentleman) who is very fond of the model and will put the time it to get it going. If you find such a person, hang onto them.
Due to its age, larger companies and more youthful menders may not be so keen.