It will depend A. on the lender and B. on what your load to value is. The higher the LTV the more they will look into it. If you have pay slips that show the additional pay is a regular item then you shouldn't have too many problems.
Best thing would be to go and see an INDEPENDENT mortgage broker who can guide you through the process. Make sure there are no stupid advice fees though and do have a damn good shop around for any insurance products you may buy as price differences can be huge.