A good specification pool of 25″ fiberglass filter, 0.75hp pump, all pipework and fittings with 2 skimmers, 4 return jets, vac point and 2 bottom drains, cost £1850. Don’t think this is a low quality installation all the pipework is BS/EN1452 standard and the pumping equipment TUV and CE certification.
The above is of course in addition to the cost of the pool tank but depending on the type of construction you choose and the finish of the pool walls, liner, tiled etc, toppings for the pool edge and landscaping is entirely down to your pocket. The normal structural engineering rules need to be applied.
Many pool construction companies don’t have JCB diggers, brick & concrete layers, tilers and electricians, they bring these trades in so why don’t you organise it yourself.
Some tips:- For the ground works (digging of the pool) a local groundworks company is often the best option. The concrete slab needs to be a C35 structural mix, steel reinforced with protective membrane and insulation. The current material cost of this base should be no more than £1000 for the 8.5×4.5m X200mm deep slab.
There are 3 main types of pool tank construction. Shotcrete, shutter and pour and laid block. All 3 must have steel re-bar reinforcement.