18 customers since March, is this all through leaflets?
I would suggest ordering 20,000 from ebay. You can get these for about £250 I think and set yourself the task of delivering 1000 a day for a month. At an educated guess, I'd say you would get about 80 customers out of this. At approximately £10 a house. There's £800 a month give or take.
This is only a guess going from the 0.4-.5% success rate I got from my leaflets. But if you did manage to do that 4-5 times then you'd hit your target. However! That's just a theory, in practise. You have to find a way of delivering 100,000 leaflets whilst doing all the first cleans, rainy days, flat tyres, locked gates, dog muck, washing lines......the 'one off brigade'......