This might not be what you want to hear, but I wouldn't bother spending that much on a laptop right now.
For ~£2.5K, you'll get something armed with an i9 8c (these are hot, so prepare to undervolt), 2080 8GB (MaxP if you look carefully - faster/hotter/higher power consumption than MaxQ), 32GB RAM, 500GB SSD and 144Hz 1080P Screen. Given how few things support SLI now, it's not really worth going for a dual GPU setup IMO. Spend a bit more and you'll usually get more storage, maybe another heatpipe, maybe even a 240Hz screen, but not much more, certainly the 2080 Max P is the fastest currently released mobile GPU so the only difference there is better cooling or a slightly higher power cap in VBIOS, but essentially same chip.
With rumours of a 2*** Super Laptops coming, I'd ball park the 2.5-3K region, and save the extra £1-1.5k towards your next machine and then either get something with a 2080 Max P, or hold out and see if the Ampere 3080 or 2080 Super Laptop chips appear in the coming few months
I would also recommend going 1080P in the machine, and then buying a 1440P/4K external screen. More flexible (as you can change the machine and keep the screen) and frankly on a 17.3" or less chassis, you only get so much mileage from a higher res screen, but it consumes a lot more performance (ergo more heat and noise) to maintain similar framerate. Laptop 4K screens in most cases are also only 60Hz.
A 2080 MaxP powered machine (NOT a MAXQ) will handle anything you throw at it even maxxed at 1080P, and many things at decent settings and framerate in 4K, its roughly a 2070-2070 Super in desktop equivalency.
Again, with the slow death of SLI, I can't really see the benefit of going much higher in price.
Paid just over £2.1K in the Black Friday Sales for my machine in spec (had 15% off); can't really see you'd get THAT much more even for double the price, not until new hardware comes along!
The only other option is grabbing one of the machines that is essentially desktop components crammed into a mobile chassis, these will be faster, but there are usually heat and power restraints, and again, yes it'll be faster, but it won't necessarily offer you that much performance for a rather substantial cost difference, IMO, that would be better put towards the next machine, when you feel the current one getting slow.