Recently I bought a Halfords sponge and it wrecked my paint job.

Sponges are in fact abrasive and should not be used to clean your car.  You can check the damage they do by brushing them across a the shiney side of a CD.

Everyone should be using a lambswool mit and rinse after every application of soapy bubble.

Avoid using an aquablade also or these plastic blades to remove water.  Clean chamois or similar.

If you have wrecked your paint job, you can hopefully polish out the defect as I have with Poorboys SSR1 polish - even a cheap polisher will do the job from Halfords.  Just be careful as you are actually removing the clear coat as you polish the scratches out (the scratches are in the clear coat typically).