Or i could just add a bit of 15mm pipe with ball valve to the lowest point through the wall to drain it.You'll burn through that and more trying to construct and maintain a brick-built bund. It needs to be completely watertight, and any rainwater that builds up in it needs to pumped out into containers and taken to a specialist disposal site for contaminated water, which will cost you time and money. Alternatively, you can build a big enough roof over it to prevent rain getting in, but no combustible materials may be used in the roof's construction, so realistically it has to be all-metal. If you can do all that for under £600 I'd be very very surprised
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local