Raising funding from private investors continues to be the single biggest challenge facing Irish start-ups, according to Scale Ireland research. In the lobby group’s largest-ever survey of start-up founders and CEOs, with 340 respondents, 50.3 per cent of respondents said funding is their biggest issue, dwarfing the 16.2 per cent cost of doing business, recruitment and retention of staff which is put at 13.2 per cent, lack of expert advice and support at 8.2 per cent and tax and regulation burdens at 6.8 per cent.  A total of 79 per cent of respondents said that attracting private capital was either…