I'd give up trying to contact the company. Although it's a legitimate business registered at Companies House, their registered office is just a firm in Eastleigh that provides a mailing address for businesses. They're trading illegally by not providing a physical address on their website and they're in contravention of the rules on UK domain names by not providing their contact details on Nominet's Whois look-up service.
Despite saying that it's a UK-based firm, it seems to be that in name only. (i.e. it's registered at Companies House but actually run from overseas). The guy running it is German and appears to live in Germany but the firm was originally set up by him and a guy in China (which is probably where their products come from).
So, if they want to ignore your emails, there's probably not much you can do about it.
If SlackAlice (or another ABer) can't help you, it might be worth seeking out the help of a local model engineering society (or even of the craft, Design & Technology department at a local secondary school), as someone there should have the expertise (and equipment) to solve your problem.