Do I need to replace my brake pads on my bike?

If those are semi-metallic pads, which is OEM for most disc calipers, then you've got plenty of pad left.

Pads look worn unevenly . Sand to make even. Still good thickness. As long as not contaminated. (simple answer = go to bike shop, small labor charge)

Just need to reset pistons, then center on rotor. 

The left one has a good thickness across the whole surface, about as thick as the backing plate. The right one appears quite worn a the lower end in the pic. If it really is,  replace before it starts scouring the rotor.

Simple way to find out.  Ride on over to your LBS (local bike shop) and have a mechanic take a quick look.  They probably wouldn't charge you a dime.  

Already asked & answered.  Even awarded me "Favorite Answer" with 5 stars.  ⭐⭐⭐⭐⭐   /question/index?qid=20201...  

Better pic this time.  One thing concerns me.  What's that little burr on the upper part of the left side pad?  Doesn't look natural.  It's time to do one of two things...or both.  As previously suggested - take the dang thing to a BICYCLE SHOP!  Let a certified mechanic get a closer inspection.  Just type into Google the words "bicycle shop" along with your 5 digit zip code or postal code in the U.K.  Brings them all up in your area.      

If not that...then learn from the Park Tool Repair Help website.  https://www.parktool.com/blog/repair-help

Disc Brake Service and Repair - https://www.parktool.com/blog/repair-help?query=&a...   Fifteen articles all with embedded YouTube videos on disc brake service. 

Last thought...  They appear to be hydraulic disc brakes.  If they feel spongy, you could have an air bubble or pocket in the fluid.  I WOULD NOT attempt to bleed the system yourself.  Let a pro do it.  If one drop of brake fluid gets on those pads, you're...  See pic below.