Hi MG, a lot depends on what information you want for analysis purposes and for tax purposes. For instance, are you VAT registered in your current Sole Trade business? If so you may want to consider another trading vehicle for your tiling so you don't have to add VAT to estimates. Also, if you are not VAT registered, will the tiling "arm" of your business push you over the VAT threshold?
If neither of these apply and you are doing your book keeping in such a way as to be able to distiguish income and costs easily for each part of your business (essential to know where your profit or loss!! is coming from) then by all means keep them together.
Also, not a good idea to have business records running through personal accounts. If the tax man wants a "chat" he normally only has access to "business records" initially i.e business bank account, if you run through you personal accounts it gives him carte blanche to check over every bank account you may have. Not good if you are trying to hide "cash" sales. Something I couldn't possibly condone of course.
