THE GA airport for London. No handling required, but the ground staff is very helpful, anyway. Very professional. Customs is quick, but fill out the General Aviation Report (GAR) form beforehand to make it quicker (on-line: https://contact-ukba.homeoffice.gov.uk/customs-travel/beforetravel/general-aviation/
Time into London City is quicker than from Heathrow. To the West side, takes longer. Taxi to local train is apparently the economical alternative. You end up at Victoria station, in that case.