After about 18 months after seperating from my x2b, my mother gave me £12K to pay of all debts. (Luckily x2b and I have no joint debts) This will show up when i attach my bank statements as i paid the cheque into my current account. Do i declare this when filling out form E. Will my x2b be entitled to any of this money?
Unfortunately as you have to put last 12 months bank statements in along with your form E, then it will show up anyway. You could always put it in the "debt" box and treat it as a "loan". All debts whether they are in your name or not are actually "marital" debts. So if you can show you have used this money to pay of all debts incurred throughout the marriage then the 12k "debt" could be seen as hers aswell as yours. Although borrowings from family members are seen as "soft" loans. (I.E. they are not likey to attract interest and if you default on a payment there are no penalties, such as borrowing from a bank say.)
It could in fact be a bonus for you should you wish to treat it that way!