I know wheel building isn’t for everyone, but I built for this much, 24/32h “Mr_ride” hubs from ebay, halo aerorage rims, ACI DB SS spokes from cyclebasket. Weigh 1550g. Easy to maintain too with normal spokes, easy to replace rims and sealed bearings.
This +1, for £150 and those hubs/spokes you’ve got a huge choice of rims available within budget.
Although (IMO) the whole process is easier with a proper wheels stand (£50 s/h) and tension gauge (£60). You can do without, but they do take a bit of guesswork out of it.
From the factory wheels I’d go for shimano, they weigh about the same as everything else for the same money, but the hubs are where the weight is so you get a much lighter rim which is where it counts. have a look s/h, I picked up some R-550’s for £30 as serious roadies with new bikes tend to already have nice and training sets of wheels so the sell on the low end OEM wheels.