How to get a param from an ajax request in twig?

Question

Ok this has been puzzling me for too long now! I have some code that makes an ajax request:

reqAjax: {
    type: 'get',
    url: '/mytemplatefolder/myfile.html',
    data: {town: 'bournemouth'}
}

This returns a json object to populate dates in a calendar. The dates have links to the town the event is in but to do this dynamically I need to be able to make use of the town param in twig. What I have at the moment at the top of myfile.html is:

{% header "Content-Type: application/json; charset=utf-8" %}
{% header "Access-Control-Allow-Origin: *" %}

{% set town = craft.request.getParam('town') %}

But town is not being set. So I guess I am missing something on how to get the data from the ajax call and set it in the template. Any help much appreciated.

Cheers