I need to link Epos Now, Xero and 2x Woocomerce & Ebay

We sell items on the following platforms
Instore-Epos Now
Online-Ebay & Amazon to follow later
Website Retail and Wholesale 2 seperate Woocomerce websites
Invoicing-xero


We need a plugin, a spreadsheet, anything that can link these together, we currently use Xero to create invoices for trade orders as its easy to link payments and send statements , I'm wondering if we did this via the wholesale woocomerce website is there a way to link the orders to the customer and still send statements separately ?
We need stock levels integrating, not all website products are on Ebay just most as the main items can't be sold on Ebay.

We are currently and have for 2 years been using Selro, but its constantly re setting stock levels, changing prices and stock levels, removing items from the sites, its causing more hassle than its helping. We don't use selro for printing/dispatch we do it per channel so there is no issue loosing that.