Hi Zeef,
If you are from an EU country there are no restrictions on your employment in the UK under the free movement of workers, moreover said company cannot be seen to be discriminating against non-national pilots.
If you are from a non –EU country, you would as already stated by Adios and AeroUK need to apply under the tier system, usually this would be under Tier 1 HSMP (Highly skilled migrant programme) however as I’m sure your aware at the moment securing employment in the profession is very difficult at the moment. Therefore unless you have secured employment or are willing to front the cash to support yourself whilst you look for work you’re up the creek without a paddle I’m afraid. Regardless you would still require a visa to enter the country and then only have a 6 months visitors visa issued initially. Securing work would be initially very difficult and you would be breaking the law if you began working under the visitor’s visa anyway, hence the HSMP Tier 1 requirement.