you can ask your tax office to send you a printed copy of your calculations and summary of account but it takes around 3-5 days from when you submit for the data to be officially filed and accepted so if you have only just done your return for last year you will need to wait a bit.
as ever this time of year is one of the busiest for hmrc as many people file at the last moment so you can also expect a delay in response time from hmrc as they will be inundated.
some lenders are more flexible in what evidence they will need, i know of some that will take business bank statements and accountants projections of income - but this varies widely with each lender and generally speaking the higher % you want to borrow, the more evidence a lender will want - nomatter whether you are self employed or PAYE.