Getting a mortgage has always been slightly more hassle for company director/shareholders than for the employed or self-employed. An employed person's income is easily assessed from payslips and P60s, a self-employed person's from their accounts and tax return. A mix of salary and dividend is harder for a mortgage adviser to assess and understand - but you can generally get to a department within a lender who understood and dealt with such applications.
Historically, many or most lenders, when considering a mortgage application from a company director/shareholder, would take into account a) salary, b) dividends taken and c) profit that could have been drawn as a dividend but wasn't (retained profit).
It seems now that most lenders will only take into account a) and b) and ignore retained profit. We're reliably informed that there are now only three lenders who will take into account retained profit as well.
Many company owners don't take anything like the dividends they could, as they want to (prudently and legally) shelter income from higher-rate tax. However, if you do that and will be looking to get a mortgage in the next few years, you might want to at least think twice about that policy. Your favoured lender (and maybe, in a year or two, *all* lenders) might only take into account dividends that actually *have* been taken, as opposed to dividends that *could have* been taken but weren't. You could consider biting the bullet and starting to pay yourself higher dividends to make yourself "mortgage ready" and able to borrow more in future. You may have to demonstrate two years of earnings to the lender, so plan ahead. It would be frustrating to be assessed on income of £40,000 when you could have been assessed on something much higher, and could easily service the debt.
This may not apply in your circumstances, but it could be really important for some people. Talk to a good mortgage broker if you think it could be an issue for you - we're very happy to recommend someone if you don't have an adviser on hand.