If you run your own company just go on the books yourself for 3 months and keep the pay slips. You'll have to pay your tax, NI, etc upfront but you've got to do it anyway in the long run - once you've got around 3 months payslips it should be pretty easy to get a mortgage - all they want to see is that you've got money coming in to pay for your loan. Once it's gone through go back to being self em!
why
If you only have 3 months payslips most lenders will require employment history for up to 3 years previously. Also, don't think that they would go with this way of proving income as you would be giving fraudulent information to acquire credit and that is a no no!
If you have had a longstanding bank account. speak to that bank first.....they are now competitive with mortgage rates and if you have shown a steady income with them, that will stand you in good stead. Usually 3 years audited accounts are required for Self employed, but again if you go to your main bank they may just be able to bend their rules a bit. Self Certified, keep away unless you have 25% deposit or more, the rates will be more and the deals available less.
Sort out in your own mind what you can afford on monthly mortage payments, and be realistic. look for a good fixed rate that achieves that amount, if possible get a fixed rate for 3 or more years, but watch out for transfrability and penalty clauses. Your own bank probably has a mortgage consultant, speak to them, the advise will be free!