Basic gear: Apeks is generally loved in the UK. Mares also has a good reputation, but that varies regionally depending on their quality of service and customer/product support. Old school die hards (& strutters) tend to buy anything Scubapro.
It usually depends on who you dive with and your style of diving. One shop can be anti-mares while another is anti-aqualung.
Get the best you can afford for your style & type of diving & make sure that it is comfortable in your mouth. A few I had borrowed/rented were too heavy and my jaw ached. So I was lucky to get to try before buying.
Have you thought of buying in the US? The prices are much cheaper, even minus VAT. & shorter distance to send for service.