So for upto £800 realistically your looking at an entry level gaming laptop that will do the job, your looking at laptops with 8gb of ram a good enough processor and a dedicated gpu, i am confident that it will play fortnite nice and smoothly with laptops upto 800 quid @ 1080p.
Speaking from experience my laptop which has very similar specs (3550h,8gb rx 560x gpu), plays games that require more power at around 30-40fps average so yea regarding the games minimum spec requirement when compared to my laptop which does not match the minimum requirement.
Dan