Thanks for the quick reply! It's reassuring to hear withholding tax shouldn't have the large impact I thought it might.
On trading through a limited company, I'm planning on doing it that way rather than as a sole trader for the reassurance of having limited liability and not being personally at risk should anything disastrous and unforseen happen. I think that peace of mind outweighs the slight increase in cost and complexity - unless there is something else I am not considering!