Saving up a 10%, £40k, deposit while renting here is quite tough though, even on 70k. And most devs don't earn that much
The median cost of a room in a flatshare in Zone 1/2 is just under £700 month, that's £8.4k/year. Let's assume other costs of living to be £10k/year that gives us a total of £18.4k/year.
Let's say you want to save £40k over 4 years, so 10k/year, that would require a take-home salary of £28.4k/year which implies a pre-tax salary of 37k.
37k should be comfortably achievable for a software developer 1-2 years out of uni.
But if you rent in the suburbs you can get a similar discount on rental as you get on purchases.
(Although the 3-bed was just an example obviously you can get a 1-bed for a cheaper price as well)
And you still have to add the expenses on top. Food, transport, council taxes, utilities.