Mapping domain name to a sub-folder

I have hosting through 123-reg and have multi-sites (not all wordpress) uploaded into sub-folders. In the past, I have simply mapped the domain names to the specific sub-folder with no problem.

However, when mapping inspirationbeads.co.uk to the inspirationbeads_wp sub-folder, the path in the address bar is showing the address of the root folder. For example https://www.daveb.co.uk/inspirationbeads_wp/product-category/earrings/ instead of https://www.inspirationbeads.co.uk/earrings.

I’ve searched the forums and found a number of helpful hints & tips, which have unfortunately not worked. 123-reg have suggested purchasing another hosting package and having WordPress installed in the root folder, but I find it strange that my other sites work ok and the WordPress install doesn’t. Any help will be most appreciated.

Thank you