A few thoughts from someone who is a serial card tart (I bounce from 0% card to 0% card), who got into debt out of necessity (two unplanned children
) and who at last has it pretty much under control:
DO NOT add it to your mortgage. It's madness to turn currently unsecured debt into secured debt. If the shit hits the fan you could lose your house!
Re the £1000. It should go towards the debt BUT if you have accrued the debt because you've had no money put aside for emergencies/rainy days such as car repairs, unexpected dental bills etc, then you MUST change that or you will not get out of debt. So use some of the £1000 to start up a little rainy day fund, how much is up to you but I'd probably say £300. That's six second hand washing machines, so plenty for a start. Then use the remaining money to pay off the card charging the highest interest.
The rainy day fund you start should be something you budget towards monthly. So if is starts with £300 in it you might want to budget perhaps £20 or £30 towards it each month going forwards. There is no benefit to paying more off the cards if you are having to then borrow it back again when things go wrong. Although in general it makes sense to use savings to pay off debts, that is only the case if you are not continuing to accrue more debts. Get the budget right in the first place so you can actually afford the rainy days and the debt will truly start to go down instead of fluctuating.
Onto card management - www.moneysavingexpert.com/credit-cards/ is the bible for checking out your options when low rate deals end. Never sit on a high rate unless you have no alternatives, and this site will give you an idea of what alternatives you have. The forums are also fab. ALWAYS sign up for online banking for each card and get into a habit of checking really regularly. The more you are aware of the balances, payment dates etc the better.
I cannot enthuse enough about www.youneedabudget.com/ and it is genuinely a worthwhile £30 outlay. The free trial is great and it has made a big big difference to how I view out budget. It is a way of budgeting which works with what you have instead of most budgets which allow you to idealise and then fail each month. And their forums are also really supportive and friendly. Just be honest with yourself - you don't want to budget £10 a month all year for children's winter gear but if you don't, it will bite you in the arse.
IMO it is better to have a longer projected time to be debt free but be realistic than to say "I can be debt free in a year if I pay X amount each month" and then fall on your face when your kids need winter boots. I know from experience, this is the first year ever I have had a budget I could stick to and felt truly in control without impending panic. And £20k student loan aside I still owe nearly £3k on cards so it's damn good to feel no panic for a change!
Good luck :)