I would suggest the Lensmate Fuji X-T5 Folding Thumb Grip over fixed versions to keep dial access, and definitely get SanDisk Extreme Pro 128GB UHS-II V90 SDXC cards for those chunky 40MP files.

Just found this thread and tbh I was pretty disappointed with how the X-T5 feels in the hand after a few hours of shooting. @Reply #2 - good point! Soft shutters are basically useless and I actually had issues with one getting snagged and nearly ruining my day. Total waste of cash. Unfortunately the native Fuji grip is way too expensive for what you actually get so I ended up looking elsewhere. The SmallRig L-Shape Grip for Fujifilm X-T5 4136 is way better for the price and gives you much more to hold onto without adding a ton of weight which is huge for street photography. A traditional neck strap was also just annoying for a city trip. London is crowded and having the camera swinging around constantly was not as good as expected. Switching to the Peak Design Cuff Camera Wrist Strap Black made things feel way more secure when weaving through the crowds. Since you mentioned the weather sealing... honestly dont trust it 100 percent in a proper London downpour. I had some moisture issues on my last trip before I started using a decent protector. Picking up a Hoya 58mm Fusion Antistatic Next Protector is a smart move. It saves you from constantly cleaning the actual lens element when it gets misty or dusty out. Its way more practical than a thumb grip that just gets in the way of your dials and saves your budget for more useful stuff.

Regarding those soft shutter buttons, I actually stayed away from them after reading some horror stories about people snagging them on camera bags and snapping the whole shutter assembly. Since the X-T5 has that nice weather sealing, sticking a screw into the thread might technically create a gap or just put weird stress on the mechanism if it gets bumped. I prefer keeping it stock to be safe, especially when traveling. For London, youre gonna want some basic protection since the weather is so unpredictable and street photography means lots of moving through crowds. I learned that the hard way when a metal zipper on my coat scratched my last screen while I was just walking around. Here is what I usually carry for peace of mind:

• Expert Shield Glass Screen Protector Fuji X-T5 for the LCD. It doesnt affect the touch sensitivity and keeps it mint if you ever decide to sell it later.
• Peak Design Slide Lite Camera Strap SLL-BK-3 because the stock Fuji strap is kinda scratchy and feels a bit flimsy for such an expensive body. The anchor system is really secure.
• Fujifilm NP-W235 Li-Ion Battery as a spare. That high res sensor and the IBIS definitely chew through power faster than you would expect when you are shooting all day. I also keep a Giottos Rocket Air Blower Large in my bag at all times. Dust shows up way easier on these 40MP files and it is a lifesaver for a quick puff of air instead of using a shirt tail to clean the glass. Better to be cautious with the new gear...