Anyone know how to stop cats weeing in my basement flats doorstep or an effective way of cleaning up after they have... seem to spend weeks trying to get rid of it with bleaches etc
The scent of lemons is supposed to put cats off - you can use actual lemon juice or lemon scented cleaners. Do not use amonia based cleaners as the cats just identifies this with urine and will 're-claim' the area with it's own urine.
You can get a powder which is impregnated with certain essential oils which are supposed to discourage cats - it worked for me in my old garden where I had cats pooing by the front doorstep. You can get it from Focus or B&Q
This may be a bit of a pikey solution, but the sound of plastic scares the hell out of cats I've encountered - plastic bag hung up by your door, perhaps?
Most household cleaners contain aromas that actually mimick cat smells ( but only a cat can smell them) - so using them may be acting as a postcard to the cat nation. However ,biological soap powder in solution can erradicate those smells and leave a clean surface which will not attract cats back again .