Thanks all, will try ur suggestions, bar the lion poo as i live too far from dublin. My neighbour is a single mother with two small kids so i don't think she could afford 60 or 70 euro to snip it.
Apologies for sounding harsh, but your neighbour should have thought of this cost when getting a pet, its just irresponsible to be letting an unneutered tom cat wander round impregnating other unneutered females.
However, back on topic, the lion dung is a complete myth, its the urine of another predator to mark the territory that would be needed, including the urine of a male human (its the testosterone), however, as Im sure you can testify, the tom cat has to spray there often enough to 'refresh' the scent, so any other urine would need to be applied equally as liberally, not really solving your problem, as you just end up with the smell of urine of another male species in the area instead!!! I assume the lion dung dung myth has arisen as they pee where they poop so the dung is urine scented.
So rather than go down that road, have you tried bottles of water resting outside the front door? The reflection should deter him.
Alternatively, make the area totally unattractive to a tom cat, citrus smells, a water spray (like a motion sensor watering hose that you see in gardens), a motion activated loud noise, a large basin of water that he would have to traverse to get to the spraying position, something equally smelly he would need to walk through, a dog to sleep on the front step for a few days, some large prickly plants blocking the door, a layer of something horribly sticky that he will have to walk through (can be removed afterwards).....