If the house looks ok to you make an assumption that it won't cost you anything to remedy defects. Then bid as normal. If you get the house, it is subject to survey.
If you get the house surveyed now and your bid is not accepted, you have wasted a lot of money. I would also suspect that getting a survey done tells the estate agent that you are really interested in the house and they might hold out for a higher bid.
If you know that the house needs work, you could pay to get the survey done beforehand. But I would make an estimate of what it would cost to remedy and bid accordingly.
Brendan