UKC

I have found a viaduct near by to me where I can practice boulder typer problems and lateral traverses. However it is a listed building, I have had a look online and the only thing I can find that is similar is new mills tora but that's a bolted established route. Are there ethics against what I am doing or rules to follow like leave no trace by cleaning any chalk residue? Any opinions or advice welcome, only been climbing 1 year and this is the first outdoor climbing.

You should be OK so long as you're not harming the fabric by kicking hell out of it or chipping holds/mortar etc. They were built to carry trains so they're pretty tough structures. I've swanned around on a few viaducts in the past and it never occurred to me whether or not they were listed although undoubtedly they were (eg the awesome Ribblehead Viaduct).

I pulled off a chunk of a 2000-year old wall in Palmyra Syria (don't ask) while bouldering on it in the 1970s. I am claiming a record. I crashed to the ground, damaging my leg and had to go to a hospital with it back in Damascus 

Not my finest hour

The viaduct is owned by someone, and just like climbing on a natural feature they may have concerns about their own potential liability if you were to be injured. A "leave no trace" approach and not drawing attention to yourself is therefore a sensible as well as an ethical approach.

Obviously you should avoid causing any damage, and fixing anchors of any kind is a no-no.