My advice - learn to change the oil yourself. Its not rocket science and takes just 10mins. Buy good brand of engine oil with the grade as prescribed in your motorcycle manual. Fully synth oils for regular commuters does not offer much benefit when thinking from the drain intervals vs price angle. Might as well buy some good mineral oil and stick with it. Since you say you are used to filling up petrol from Shell, might as well get their Shell Advance 4stroke oil. And stick with the drain interval prescribed in your manual.