Dear Sir,
We will use Open source Based Backend Platform (Zend Framework, PHP and My SQL) and Use HTML5, JavaScript and CSS3 for the Moonpig resembling site.
If required, we may use Flash in the Web development. but that will be our least preference.
Using HTML5, CSS3 and JavaScript will enable this application to work well on the iOS devices also which do not have flash in them.
Please see PMB for further details with links to sample websites.
Warm Regards,
Vishaal Vij