Bank statements for visitor visa sponsor thing - regarding overdrafts?

[Terpe]

Iani,
It's true that the visitor visa has somewhat different approval criteria to other visa's. But don't get too hung up on that. I'm sure you know that the overall objective from UKBA is to prevent people entering UK who have no intention of leaving, and every intention of staying as an illegal immigrant.
Applications for a visitor visa needs to have the objective of the proving the opposite. That can be done in a number of ways.

My advice is to always apply and to submit the most convincing application you can do. The risk in terms cost is very small (I think around £76).

From the information you have divulged I wouldn't see any problems.

[joebloggs]

From the information you have divulged I wouldn't see any problems.

but they are a lottery, just don't expect one, but it would be a nice surprise if you get one

[Terpe]

but they are a lottery, just don't expect one, but it would be a nice surprise if you get one

Yes, it can be seen as a 'lottery'. Mainly due to the fact that the ECO is not following a strict protocol, the decision is totally discretionary depending on what the individual ECO believes about the individual application (rightly or wrongly).
Although there is no appeal route against any refusal, the cost is very low