Thanks for your thoughts JieJie..
I suppose that there may be problems as the Invite is our sister company in China, for whom we provide technical training whilst project managing the installation. None of us reside in China and pay tax in UK and this is accepted via the dual tax exclusion policy between UK and China.
He did marry a Chinese national last year, so maybe that has totally complicated the situation.
Another technical adviser has just received and new business visa at beyond the grey hair age of no hair at 76.
Even myself with 10 years of multi entry visas, find that they can be totally different. 6 Months 60 days, 1 year 30 days, 1 year 90 days, always totally confused by what I ask for and what I receive. There appears to be no set formula for this.