First home, and a credit file you are worried about.

The things that worry people most, in order

A small default from years ago. Usually the least serious thing on anyone's file, and it is remarkable how much anxiety it causes. Its age and size are what matter, and a £90 phone default from four years ago is seldom, on its own, what stands between you and a mortgage.

A thin file. The opposite problem, and genuinely common among first-time buyers: never having borrowed anything means there is nothing to assess. It is fixable, though not overnight — a small amount of well-managed credit over several months builds a record where there was none.

Buy-now-pay-later. Increasingly visible to lenders, and worth being careful with in the six months before applying. Not disastrous, but heavy use of it on bank statements reads as reliance rather than convenience.

An overdraft that lives at its limit. An underwriter reading three months of statements notices a balance that never goes positive. It affects the affordability arithmetic more than people expect.

Where the deposit comes in

Being honest: with adverse credit and no mortgage history, the deposit is the lever that matters most. It is the difference between a narrow choice of specialist lenders and a wider choice of mainstream ones. If you are six months away from a bigger deposit, that six months is often worth considerably more than it feels like at the time.

That includes gifted deposits from family, which are normal and perfectly acceptable — though the lender will want to see where the money came from, and a letter from whoever gave it.

What to do in the six months before you apply

• Get all three credit reports. They differ, and lenders do not all use the same one.
• Dispute anything that is wrong — it happens more often than you would think, particularly after a house move.
• Register on the electoral roll at your current address. Small, free, and it genuinely helps.
• Keep the current account out of the overdraft, and go easy on buy-now-pay-later.
• Do not apply for anything else — a flurry of credit applications just before a mortgage is the worst possible timing.

Ring me before you start rather than after. Half of what I do for first-time buyers is stop them doing something in month five that undoes months one to four.