Interest only is normally what you would be offered first, moratorium only for dire cases. They will need all details of your income and outgoings and if this shows, with reasonable expenses (no dearest tv package) that you can only afford int only then you are likely to be successful.
There is a code in which all banks need to deal with cases like yours -
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See below from the code - if you meet the requirements ( the bank will need to see all the money in and out of the house - they will also want to know whats going to change to so that you pay the increased payment once the payment break/interest only period etc is over)
Such alternative repayment arrangements must include :
a) an interest-only arrangement for a specified period;
b) an arrangement to pay interest and part of the normal capital element for a
specified period;
c) deferring payment of all or part of the instalment repayment for a period;
d) extending the term of the mortgage;
e) changing the type of the mortgage, except in the case of tracker mortgages;
f) capitalising the arrears and interest; and11
g) any voluntary scheme to which the lender has signed up e.g. Deferred Interest
Scheme