There’s no real issues with this, except if you were trading in real life, how many £10K accounts could you afford - if its just 1, then 10% risk might not be the smartest move when starting out.
To add to that, when a position goes against you on a demo, you don’t feel anything. On a live account, you will be feeling it regardless of what anyone says.
0.5 lots is an acceptable size to trade on a £10K account - this is the same size I’ve been trading throughout this whole experiment.
It might be smarter to simply go in at half, using 0.25 lots - chances are it will go against you, when it does you can look to add the second 0.25 lots for a much better return.
Lot size is still important. If you set 10% as your SL - the bigger your position size, the closer your SL will be.
As you can see from the above, you could be risking 10% as your SL but the more you increase your position size the closer and closer your SL gets.