"With regards to Shop will not install Windows for you", I would like to share my experience:
I know how to DIY, has been doing since the era of Intel 80486, due to busy I got my new rig recently from SLS.
Initially went to Dynacore, the boss is friendly and knowledgeable, he even suggest me not to get Ryzen 3900X but 3700X instead. I would have gotten the rig from him if he accept Grabpay for payment.
Going thru' the list of shops that accept grabpay, I went to videopro but doesn't have stock for 3700X, took my contact number and said will call me when there's stock but I waited for 2 wks no call (even till now), can guess what kind of service they providing?
Next in the list that support grabpay is TechDeal$, their prices are on the higher side, so i showed the boss videopro and Dynacore's pricelist and he tried to match very closely. I paid a deposit of $100 and the next day he called me that the rig is ready for collection. As I didn't buy any gfx card from them, he is unable to test the rig, so I asked him to plug in any gfx card to test it out and he said ok.
Upon paying the balance, he asked his men to bring me to another shop to collect my rig. The technician unboxed everything and showed me the BIOS for cpu type/memory/disk etc hardware. I noticed the 3x 120cm fans from Tt AIO got no lights, the techician said need to install the RGB software to enable it, he asked me if I can wait, he can install Windows 10 to test it, I didn't buy any Windows from the shop and was surprised the technician offered to install to test the rig (of cos no activation).