I was in a similar position as yourself last month. I spent around 3 weeks trying to find Pylontech stock without any luck. Being in the UK it's slim pickings as you likely already know.
When I couldn't find anything I started to look at other options. I narrowed the alternatives down to -:
SOK Battery 48V100Ah Server Rack Battery
EU - Pre-order. Will be in stock in 27-May. All pre-order can enjoy - €50 discount. Contact cusotmer service to get the refund.UK - Out of stock. If pre order waiting time is too long, orders could be cancelled on request for a full 100% refund anytime prior to when the order has been shipped...
www.europe.sokbattery.com
Quoted £1784 per battery delivered DDP to the UK.
16 x EVE 280ah Cells + Seplos Mason DIY case
High quality MASON DIY Unit (suitable EVE 280Ah cell)BOX stack type without cells from China, China's leading Seplos DIY Kits product market, With strict quality control Seplos DIY Kits factories, Producing high quality MASON DIY Unit (suitable EVE 280Ah cell)BOX stack type without cells products.
www.seplos.com
Fully Matched 4pcs 3.2v Eve Genuine Grade A 280ah Lifepo4 (lfp) Cells Battery 6000 Cycles With New Terminals - Buy 12v Deep Cycle Battery new Model Cycle solar Energy Product on Alibaba.com
www.alibaba.com
17 X EVE 280Ah cells 16s + 1 spare: £2552.45 DDP.
Seplos Case + 2 x 50mm parallel cables + 2 x 50mm battery cables: £648.87 DDP.
I also tried EG4 but they were unable to arrange adequate shipping to the UK.
In the end I went with the EVE cells and a DIY Seplos Mason case. I've saved near 50% of what I would have spent on Pylontech batteries and I'll have 14.3KWH - 200A to play with for just £3201.32 delivered. I could have perhaps negotiated a better deal, but being typically British I did not want to appear rude.
I'd recommend Henry at Seplos and Amy Wan at Luyan (As would many others) if you did go down this route.