Stoner, I'm off work now (and slightly beered up) but here goes.
If you alter the lighting of your car from the manufacturers original specification without legal approval then you are effectively making the car illegal, it can also can screw the insurance too. This does apply even to classic cars when they are built to different specs and legislation compared to present day vehicles.
Moving the reflectors and fitting new turn indicators in a different position is probably a risk as the car could fail its MOT or be classified as unroadworthy if you are pulled over by the police ( if they know what they are looking at...)
Unless you get approval to do this by getting the car SVA'd and even then its not quite as simple as "I will just move them to this place as that's where I have space" However I would not recommend getting a classic car SVA'd either as it could fail on something totally different as its being tested as a modern car.
I could be wrong as I'm used to working on new cars where we have to fully homologate stuff to stricter rules
To be honest I would leave well alone and use hand signals!