best company setup for selling services

Assuming it's a low-risk and legitimate business, I'd say Isle of Man or a jurisdiction like that (Jersey, Gibraltar, Guernsey, maybe Caymans). Work with someone who provides local directors and nominee shareholding to make bank account opening easier. Costs a little extra, though. I wouldn't do it for a business making less than 100-200,000 EUR/year in profits at least. Corporate tax is normally zero, but the entities are not tax transparent.

If you want something a little cheaper, check with Gecko, ILS, Aston, and Dixcart. If you need a little more hand-holding and sophisticated services (legal help, proper tax planning), speak with Appleby, Vistra, or Sovereign Group.

You're looking at around 5-15,000 GBP/year in fees (bit more for the higher end ones), depending on size and complexity of the business. If you are able to accurately predict the workload required, you can usually negotiate a fixed fee so as to reduce the unknowns.

Would have had been helpful to know what exactly it is you are going to sell.