Wow I never knew that, can't even work out how that makes sense as both span from your name I thought.. still good fact to know, thank you.
as an ex underwriter and then financial adviser its simply an added risk factor - and risk is something you seek to mitigate - either by loading a loan or you decline.
Also I remember somebody who used to spend everything on credit card in order to get cashback and it was a massive struggle to get them a morgtage because of underwriting rules at banks (they always paid in full at the end of the month thus incuring no interest but earning points for flights etc) - some banks state that regulary spending over a certain % of income on a credit card per month is an automatic decline - others will make you seperate out mortgage, car payments, food etc and list them as expenditure and also if you have regular payments (such as a credit card each month) - which effectivley doubles the outgoings
the rules are often rigid and result in an instant decline especially if they are using a computer based scoring system.
In the end after talking to the client we ascertained that several years ago somebody had tried (unsuccesfully) to spend fraudulently on their bank account so I suggested placing a note on their credit file to state that. - The result is that once there is a note on the system people can rarely computer score it without a real person looking at the file to underwrite it - and real people make common sense judgements (some of the time at least) - Though this will result in a delay in applying for anything - store cards, credit cards, hire purchase etc!
But as a general rule avoid online bookies if going for a mortgage etc... also pay day loans as they are viewed as a sign of potentially mis-managing money
Also avoid multiple applications as this can score negatively (looks like people are desperate for credit) - now companies can do a search that leaves no trace - but they by default dont (money saving expert have a facility on their website that does so can be useful if shopping round for a credit card etc)
On top of that ensure you are on the electoral roll - make sure that you get a copy of your credit file from experian or similar before you apply and check details are correct and if anything is wrong get a mark registered on your file to show dispute - plus any linked people are relevant (and will be more likely to help rather than hinder your file)
payment records are shown for the last 12 months - i.e any payments you are behind will show for 12 months after they are brought up to date and any defaults are shown for 6 years.
basically pay all your stuff on time not using a credit card and you should be fine -
other things to note large regular payments to pubs are viewed with suspicion - I had an underwriter once question payments to the pub of around 500 per month!... turns out the client regularly used premier inns to stay in for work - easy enough to sort out as his work paid his expenses a month in leu and this tallied but a lot of people would have just taken the fact that they wanted further info as a problem and walked away from it
I rarely use online bookies but if I knew for exaple I was going to apply for a mortgage in over 6 months time I would transfer a lump sum to my online account via my bank and then bet from the online account - if it was less than 6 months away I would transfer using a credit card then pay the credit card off at the end of the month as it wouldnt show bookies on the bank statements (it is rare to be asked for more than 6 months)... but dont withdraw any winnings till after the mortgage is finalised because if it takes several months they may ask for up to date statements - also as it would be a one of payment to a credit card it could be a holiday or a tablet etc so wouldnt be classed as ongoing spending (if you transfered every month and paid off then it would - but they wouldnt see the bookies as they very rarely ask for credit card statements in a mortgage application as they can track all the spending and payments through experian / equifax)