Hi Louise
You do not need to mention VAT if you are not registered for it
You will have to do a self assessment tax return every year and it is wise to save around 15 -20% of your monthly income to go towards the tax you will have to pay in a lump sum on any profits
you will be advised to keep a profit and loss account - two spread sheets -one with all your INPUTS -These are your expenses incurred in going about your business -materials,fuel,tools etc. and one for your OUTPUTS -this is a record of all earnings. it would be wise to read up on HMCR site what you can calim for in Expenses
if you husband buys new tools to start his business -and a vehicle -he can claim back a portion of this as Tax deductable in the first year of trade.
You will price the job as a whole based on how much it will cost you in materiels and how long it will take you in man hours to do the job. The customer will either pay up front for materials before you start or you can ask for an amount on the day you start for materials.
It is wise on a big job to ask for payment in two or three amounts.
Don't expect to make a huge profit the first year as there are a lot of Inputs starting up a business.
HTH