We are refuelling helicopters by using fuel in Barrels and using a fuel pump. Can the same be used for fix wing aircraft for locations where fuel bowser is not available?
Yes, as long as the fuel container and pump are properly bonded to the aircraft and the pump is designated for use with that fuel, there shouldn't be any safety issues.
If you are operating commercially, I would check with your FBO (I'm assuming) certificate holder, insurance company, and local FAA inspector in order to satisfy regulatory requirements for fuel quality maintenance and record keeping.
Among the many rules that are readable on the Net, I suggest you to read the paragraph 6.13.of http://www.ocair.com/aboutjwa/rulesandregulations/docs/AirportRulesandRegulations.pdf?rev=7-2015