the best advice I can anyone is to look online for their decorations. They are so much cheaper and as most of us have budgets to work to it gives you an opportunity to little more crazy.
Here is an example of some balloons that I brought - https://www.ebay.co.uk/itm/274502944714 In the shops they are at least 3 to 4 times the price.
I also recommend these BoBo balloons - https://www.ebay.co.uk/itm/143519522647 They look absolutely amazing, but the only thing with these are that you need a party shop to fill them for you as they can be very tricky.