UK visa refused do to lack of economic ties in the UK. What are my options?

It was a combination of issues that led to the refusal.

Starting with the employment letter:

You have supplied an employment letter to support this. I note that this letter doesn't have a named signatory.

To which you replied:

The copy of my employment letter was not signed by me (this was a stupid omission on my part). The original is on my file with the company.

Normally such a letter in support of an application has the following, is written on company letterhead, and is signed by an authorized signatory (for example, the head of human resources, the CEO, etc.):

1. Your name (as in your passport)
2. Your identification details (for example, your passport or government id number)
3. Your position in the company (job title)
4. The length of your employment (for example, it shows your start date).
5. Your total salary

It also usually contains an indemnity clause.

In all cases, this letter is not supposed to be signed by you (I think you may have confused this with an offer of employment which is not the same thing).

You are also supposed to submit originals, or certified copies.

Next, the ECO tried to verify your employer is a genuine, legitimate business; and that did not go well either:

The contact email for the business is ********@gmail.com rather than an official, corporate email account. I also note the phone numbers provided are mobile numbers. A search through open sources has located an official website for a business called ******* in Nigeria, however the contact details on this website doesn't correspond with the details of the letterhead.

Next, the officer tried to validate your means of support during the application, and there were some issues there as well:

As evidence of funds you have submitted statements of ****bank and F*** bank for accounts in your name. However you have not sufficiently documented your employment or your income and the documents supplied support the origin of these funds. I am therefore not satisfied that these funds are genuinely available for your use or that your financial circumstances are as stated.

The ECO is saying that in your bank statements, it is not clear or obvious that your salary is being deposited, or what is the other source of the funds. As it is not clear (to the ECO) the source and nature of these funds, he/she is not satisfied that you are authorized to use these funds.

In summary:

1. The letter you supplied stating your employment was not signed by anyone.
2. The company details on the letterhead didn't match publicly available information on the company's website.
3. Your bank statements didn't show regular income as proof of the funds you had.

All these combined led to the rejection of your application. The fact that you were rejected before is on file, but each application is judged separately.

Now, what can you do?

I suggest the following; but nothing is guaranteed here, I am just stating from my experience dealing with visa applications. Even if you do all this, your application may still be rejected:

1. Show official payslips. Normally, companies deposit salaries into bank accounts directly (wire transfer, direct deposit, etc.) and issue regular payslips which show your earnings and any deductions for that period. If you are being paid in cash - then you will have a tougher time with this.

2. Provide independent evidence of the existence of the company; however normally such documentation is not necessary as company information is usually public. In your case, the companies details are in question which raises immediate red flags. Therefore, I would try to provide some third party supporting documents. These could be in the form of a letter from the chamber of commerce or business registry, a copy of the business license (which is properly notarized), etc. or a letter from your company's law firm.

3. Your bank account should correspond to your income. Do not borrow funds to pad your account. If you have any unexplained deposits (for example, a separate bonus) these should be explained if on the bank statement the narrative is not obvious.

See also: My application was refused due to 'lack of evidence of funds', are there hidden requirements for UK visa applications? for other tips