Ask an Immigration Solicitor. Get an Answer ASAP.
Thank you for the question. It is my pleasure to assist you today. Please confirm from which source the other income will come from?
An individual in the UK as a representative of an overseas business can only work full-time as a representative of that overseas business.
If the income is not from working for your own business, ie funds owned to you by the company, then this should be ok.
Should you lose your job the Home Office may start the curtailment process, which means shortening your visa expiry date as your circumstances have changed. The curtailment process can sometimes be delayed and you could potentially stay in the UK until this happens.
You should only be working for the overseas parent company.
You should be working full time for the parent company. I suppose you could do this free work outside your working hours.
No worries and all the best.