I am not sure how the event details (form) is supposed to interact with the assets. Leaving this asside, one possible scenario could be to actually use the e-commerce module. Each webapp item (asset) can be a product. Not only can a product have all that you have outlined in your image, but you can also define sets of attributes. Going further, you'll actually have a cart where you can add and remove as many items as needed, previously configured via their attributes. If payment is not necesary, on the checkout form you can only leave get quote option available (the button is customizable, you can have you own "Arrange Delivery" button in place), this wil process the purchase without collecting payment. Once "purchase completed", the admin and customer receive an invoice containing the product description (with attributes as well) and iwth a summary of the checkout form field values. Futher details like those present in your event details form can probably be included in the checkout form.
All the above can be implemented inside a secure zone, so providing the user with the option of logging out after the purchase is easy enough.
Hope this helps,
I've now adopted the method you've suggested.
My next challenge after customising layout etc, is that I need to have more than one "shop" attached to the main site.
Each in its own secure zone, one for each of our clients who require this service.
Is it possible to have more than one shop attached to a site?
You can have more than one secure zone on your site, and inside each secure zone you can assign a single catalog from the e-commerce module.
So only users registered to a particular secure zone can have access to the products within the catalogue assigned to that secure zone.