Planning permission on loft conversions has been relaxed allowing more conversion work to be under taken. In terms of your boiler have you considered a ?Combi-boiler?, this would do away with storage in the loft.
Picking up on your point about use, if you are going to just use the space for storage you should be able to board out on the existing ceiling joists.
If however you are going to use the space for any other purpose you should be considering Building Regulation approval, as there are many other aspect to the loft conversion over and above structure.
If you are considering converting your loft we offer a very competitive scheme design service which is offered at a nominal fee through our web site.
Our feasibility report covers all aspects of loft conversion and also advises on the overall feasibility.
We would be pleased to assist you in developing your loft design.
Please feel free contact us and we will discuss your requirements further at info@jeremywedge.com or visit our website