Ideally, to avoid any problems further down the line, all business expense accounts should be in the name of the business as opposed to individuals. It should be fairly easy to transfer the name over?
Bank accounts, there must be some business accounts out there which operate on a set monthly fee basis?
Insurance policies, again, it would be more beneficial and straightforward if these were in the name of the business.
Offsetting expenses against tax, in simple terms any direct business costs can be offset against income although you will need to be careful where equipment, such as phones, are also used for personal affairs. By the letter of the law, personal use of business equipment would be deemed to be a benefit in kind and therefore taxable to the individual.
Building materials, in order to keep things simple and unified, it would be better to have these in the name of the company.
* While I have given my general opinion of the above subjects, this information should be ratified with an accountant who will be aware of your personal situation and any changes in legislation which may impact the above comments.