How to use a response saved in an external file in an assertion to do an XPATH match for the respons

We are using a some groovy scripts to run our SoaPUI soap requests from values extracts from a database, i.e. using a simple data driven mechanism, to allow our test automation to run through Jenkins/Maven. We set the dump file to save the responses, and are looking to read these files back in again, run the soap request using the right data and then compare the contents of the soap response with the contents of the file we used to prime the test.

I'm pretty OK on doing everything through groovy in SoapUI, except getting the contents of the file into the SoapUI Soap Request, so that I can use XPATH matches in the assertion. If anyone that has done this sort of thing before has any tips on how I should do this, I'd be very grateful.