JD,
Yes, I did mine using the commmission number and here's the information fields that are provided on it.
1. Make & Model
2. Car/Chassis Number
3. Engine Number
4. Body Number
5. Specification
6. Colour: a) exterior, b) trim, c) hood (top)
7. Date of Build
8. Date of Despatch
9. Destination (Dealer)
10. Other Numbers (where recorded)
11. Details of Factory Fitted Equipment
12. Other Information
13. Issued to
14. Date of Issue
15. Signature of Archivist
Note that they do not always have all the information on every car. One of my TR4A's had much more information including key numbers, hood color, date it shipped, destination and what ship it was shipped on while the other did not have that information available.
So on the one with minimal information, I was able to confirm the chassis and engine were original, the day it was built and that it originally came with radial tires on wire wheels (which were gone when I bought it). So it's up to you whether that's worth the cost if that's all you get.
Scott