We will be able to list your book on our own store The Great British Book Shop, and all the major Amazon retailers. (United Kingdom,USA,France,Spain,Germany,Italy).
We also provide title and supply information to other retailers including Alibris, Book Depository, Gardners, PBShop & Books etc. These retailers have a network of small retailers and bookshops that could list your book, but would not be able to guarantee getting onto those.
If we are listed as the distributor with Nielsen in the UK, then bookshops and retailers should have the necessary tools to place orders with Nielsen/us.