How much to charge?

[An Exception]

I don't know much about commercial photography or it's value so I was wondering if anyone here had some advice on pricing.
I just received a call from a PR guy for Dartmouth, and he says he wants to use 3 or 4 images from an engagement shoot I did for a national ad campaign to attract people to Dartmouth, apparently he wants to be able to use the images for 5 years. The problem is I have no idea what to charge them?

Also as this is a marketing campaign, I assume I would also need permission from the couple in the pictures (which I would ask for anyway)?

Below is what he emailed to me, I've already told him I don't have any availability to shoot some specific images, so it would just be for the few pictures from the engagement shoot.

Dear xxxx,

Great to talk to you just now - as I said we are putting together a
destination marketing campaign for Dartmouth and were very impressed
with your images of Charley and Si in out beautiful town. They capture
the mood and beauty of the town so well we were wondering if we could
use individual images for the campaign, which will be used mainly online
and on railway posters nationwide.

In addition: do you do commercial photography to a brief? We are also
looking for specific images to fit a funny line of text. Art direction
would come from our marketing agency but we need a talented photographer
to fulfil the brief. We are looking for 7-8 photos, each to a different
brief. If you have availability, and its the sort of work you would
like, how long would you estimate this to take and how much would you
charge?

 

[An Exception]

A release / consent would be required unless you have that release already due to it being written into your contracts.

Even if it wasn't advertising you could still have issues for example, even posting the images on here because of the clients right to privacy.

I wouldn't think that would be an issue in this case as the client submitted the pictures to a national wedding blog.

 

[An Exception]

Thanks for everyones help.
I think I'll send a quote first before bothering the couple. If the PR guy is happy with the quote or we negotiate a price we are both happy with, I'll then ask the couple for their consent (I don't think they would object) before going ahead.

 

[An Exception]

^^^
In my contract copyright remains mine but they are licensed to share with friends/family as much as they want etc.
I actually physically tell the clients after a shoot that I will be uploading a set of the images to my blog and ask if that is ok. The blog post is initially password protected until they give the images the ok.
No model release clause though...