I would suggest the Ltd Company route. You don't have to use an accountant to set one up, plenty of places online do it very cheap. I am an accountant am I am using them to set up mine. They can also set up your business account.
Main benefits of a Ltd company are obviously limited liability. You as a person will not be responsible for any debts the company 'may' occur.
Also if worked right the Ltd company route works best for tax reasons.
You need an accountant to sign off your returns at the end of each year.
You need someone other than yourself to act as a secretary. Unless you make up names but address them to yourself.
Limited Liability? Yes that is the idea of a Ltd company, but when he is working with very little overheads, and obviously dealing with items which always hold some value, he has little to be concerned about unless he starts pulling 60k loans out of his ass.
I have been both a LTD and a sole proprietor and the ltd company isn't worth the hassle unless you are required to do so by contract.
My mother has successfully run one of europea largest classic car parts dealership for over 25 years and is yet to even come close to being advised to go LTD or LLP
If you're an accountant, why aren't you just filling the forms in and doing the job yourself instead of through an online company. The reason I did mine through an accountant is that it means I only go through the ordeal once. Almost everyone who tries to do everything by themselves to save money ends up doing it 3 or 4 times before it's completed by which point they have no desire to continue.
For me it was £250 well spent, it allowed me the job that was paying triple that on a weekly basis. I closed the LtD company so I didn't have to go through the accounts every year as well as my own tax return.
Remember as a ltd company you will have to register for PAYE so you can pay yourself from the company, you then get hit with company tax on the overal income of the company, an the further 23% income tax when you pay yourself.
Sod. That. Sole trader an work your arse off.