Well, it’s because devs Hello Games are based there.
Their office and the surrounding streets have been constructed in-game by No Mans Sky player Joan, a.k.a.
Rasdar07, and shared in the base building chat on the games Discord server.

Joans recreation of Guildford was featured in aTwitch streamby LordFrobozz, who alsotweeteda clip at Hello Games today.
Ive never been to Guildford myself, but I feel like I ought to now.
When I chatted with Joan earlier, they said theyd never been to Guildford either.

Instead, the recreation was built using Google Maps and Google Earth, mostly.
No Mans Sky’s Guildford features the Hello Games office and the nearby Three Pigeons pub.
The pub gave Joan a bit of trouble at first, but that was soon resolved.
I reached 3000 base parts before finishing Hello Games office.
However, I managed to save some base parts and finally furnished the interior.
Although the build began a few months ago, Joans PC had some issues and it was set aside.
The project was only restarted a few days ago.
If you want to visit the real Guildford then its probably worth catching a National Express.