Do a cash flow analysis of your business for a three-year period.
Remember that during growth periods fixed costs and variable costs will most likely both be higher.
Do three cash flows: optimistic, realistic and pessimistic.
Remember to budget for the increase in VAT and taxes as well.
If your cash flow shows a shortfall during the expansion period it may be necessary to consider getting bridging finance from your bank. Include this in your cash flow to show that it does bridge the cash flow shortfall.
Your cash flow should include the cost of finance (interest for an overdraft or payment for a term loan.
Build some fat into your budget by over-budgeting for expenses. If your cash flow shows that you can still make it then it means that if you incur fewer expenses you will have more money in the bank to finance the growth of your business.
Regularly measure your budget against actual figures and amend the budget if necessary.
Also, run your cash flow past your accountant to get his view on it and to make sure it is complete.