Welcome Kathy. W/o the VIN I'd have no idea how to find the car, but you might try to track down the "manufacturers in London" you mention. I assume by manufacturer you mean a dealership, and not the actual Abingdon works; the London dealership has likely changed hands, but each London borough council keeps records of all businesses (opening, closing, and transfers). Perhaps the current possessor of the original dealership's books can do some research for you, as you know the approximate year when you bought it.
I also had good luck myself on getting some specs on my own MGB by contacting British Motor Industry Heritage Trust in Warwick UK. If you can eventually find the VIN (they call it the chassis number) or engine number, they can pull the original factory record. Reach the BMIHT at Banbury Road, Gaydon, Warwick, postcode CV35 0BJ in England.
Tom