Validating Plone 3.2.1 BrowserView - paypal

Question

I have written a simple add-on browserview for a Plone 3.2.1 site, it is a simple form that uses HTML variables specified by PayPal and then posts to a PayPal address.
Due to the nature of these fields on the PayPal form, there is absolutely no validation when I post directly to PayPal, this is understandable as most of them are optional. I am looking to use urllib and urllib2 in order so that I can instead post the form to a Python script, validate the input and and then post to PayPal.
Layout of BrowserView (trimmed)
paypal.test
|-paypal
|-test
|-browser
|-paypal_validation.py
|-paypal_validation_script.py
|-paypal_view.pt
|-configure.zcml
configure.zcml
<configure
xmlns="http://namespaces.zope.org/zope"
xmlns:browser="http://namespaces.zope.org/browser"
i18n_domain="paypal.test">
...
<browser:page
name="paypal_validation_script"
for="*"
permission="zope2.View"
class=".paypal_validation.PayPalValidation"
/>
<browser:page
name="paypal_validation"
for="*"
permission="zope2.View"
class=".paypal_validation.PayPalView"
/>
</configure>
paypal_validation.py
from Products.Five import BrowserView
from Products.Five.browser.pagetemplatefile import ViewPageTemplateFile
class PayPalView(BrowserView):
template = ViewPageTemplateFile('paypal_view.pt')
def __call__(self):
self.paypal_name = getattr(self.context, 'paypal_name', 'World')
return self.template()
paypal_view.pt
<form action="paypal_validation_script" method="post"
tal:define="did python:request.form['did'];
ourl string:http://www.mysite.co.uk/uploadedfiles/;
dil python:ourl + did">
<input type="hidden" name="cmd" value="_xclick" />
<input type="hidden" name="business" value="paypal-facilitator#someothersite.co.uk" />
<label for="item_name">Design Name:</label>
<input name="item_name" id="item_name" />
<label for="dimensionx">Width (mm):</label>
<input type="hidden" name="on0" value="Width (mm)" />
<input id="dimensionx" name="os0" />
<label for="dimensiony">Height (mm):</label>
<input type="hidden" name="on1" value="Height (mm)" />
<input id="dimensiony" name="os1" />
<label for="dimensionz">Depth (mm):</label>
<input type="hidden" name="on2" value="Depth (mm)" />
<input id="dimensionz" name="os2" />
<label for="design_no">Design Number:</label>
<input type="hidden" name="on3" value="Design Number" />
<input id="design_no" name="os3" />
<label for="tool_no">Tool/Cutter Number:</label>
<input type="hidden" name="on4" value="Tool/Cutter Number" />
<input id="tool_no" name="os4" />
<input type="hidden" name="item_number" id="item_number" tal:attributes="value dil"/>
<label for="street_addr">Street Address:</label>
<input type="hidden" name="on5" value="Street Address" />
<input id="street_addr" name="os5" />
<label for="city">City:</label>
<input type="hidden" name="on6" value="City" />
<input id="city" name="os6" />
<label for="postcode">Post Code:</label>
<input type="hidden" name="on7" value="Post Code" />
<input id="postcode" name="os7" />
<label for="tel">Telephone Number:</label>
<input type="hidden" name="on8" value="Telephone" />
<input id="tel" name="os8" />
<label for="email">Email Address:</label>
<input type="hidden" name="on9" value="Email Address" />
<input id="email" name="os9" />
<input type="hidden" name="amount" value="19.99" />
<input type="hidden" name="no_shipping" value="0" />
<input type="hidden" name="no_note" value="0" />
<input type="hidden" name="currency_code" value="GBP" />
<input type="hidden" name="return" value="http://www.mysite.co.uk" />
<div class="formControls">
<input type="submit" data-env="sandbox" value="Pay with PayPal" />
</div>
</form>
paypal_validation_script.py
This is currently empty as I have so far been unable to get this working... I presume I can just use context.REQUEST here to obtain filed information?
What is happening
Whenever I submit the form I am taken to a 404 explaining that paypal_validation_script is not available, I'm not sure how I can reference this script (see above) in my form so that I can validate and post the necessary information using it.