Robert,
Thanks for the reply!
The main reason for changing the title/description tags with javascript was to make the pages more indexable (and readable on google). Would you say these pages will provide any SEO benefits to the rest of the website? Or would it be better to set a nofollow tag?
I will have a look into speeding up the property pages however it's most likely because the information is being rendered on our software providers server which at the same time is probably handling 1000's of other requests aswell