Means tested charity payments. Do I declare them ?

[willowtree]

I am fortunate enough to have been granted a means tested payment from a charity to help with the cost of raising my child single handedly. It is referred to as a Termly maintenance allowance by the said charity and, as the phrase suggests, is paid 3 times a year in line with school term times i.e. september, january & may.
I claim tax credits and also do tax returns as I am self employed.
Do I need to declare these payments and will I a) be taxed on them and, b) have my tax credits reduced, bearing in mind they are means tested and take into account my earnings and tax credit payments?

Thank you