When I studied my Air Law (3 years ago) the rules stated that if there were up to 4 people on board then the costs could be shared equally between the pilot and passengers, i.e. ¼ each. If there were more than 4 p.o.b. then the pilot must pay for it all (i.e. no shared costs!)
So, to stretch a point but to stay within the law, the sponsoring company could reimburse your (up to 3) passengers costs but, alas, not yours as the pilot (you must pay your share).
I'm fairly sure things haven't changed since my studies, but I'd get CAA confirmation if you want to be sure that you won't break the rules.