IS IT POSSIBLE TO GO BY TUBE WITH WHEELCHAIR FROM ST PANCRASS TO WESTMINSTER?

i AM DISABLED I WOULD LIKE TO ASK IF ANYBODY CAN ANSWER MY TWO QUESTIONS.i WISH TO GET TO ST PANCRASS TO WESTMINSTER WITHOUT ANY STEPS IF POSSIBLE, i HAVE TO GO FROM ST PANCRASS TO TILBURY DOCKS. VIA FENCHURCH ST STATION. ANY IDEA HOW I CAN DO THIS PART TAXI PART TRAIN? I DO NOT LIVE NEAR LONDON.THANKS FOR ANY ADVICE