Computer repair

Hi I came across this forum and I'm looking for some advice, I have taken my PC in for repair, we thought the problem was a faulty PSU, we told him what symptoms were happening and the repair shop said it could be one of 3 things, mother board, psu or hard drive, after 4 days the repair shop said none of the symptoms we said were happening had happened while they had it.
so we left it a bit longer so they could look into it further, a few days later I called again, this time they said they had tried to do a bios update and now they could not turn on the PC, this was not what was happening in the first place when we took it in, I asked why they had done updates to mother board when nothing had happened while they had it, he said that was what was causing the symptoms we described in the first place, so he decided to try update, they said we now needed a new mother board, which we paid for.
We took it home and after a few days the same symptoms re occur that we originally took it in with, we go back and this time he says it could be PSU, we pay to have new PSU fitted, since the PSU has been fitted everything has been fine, My problem is I have paid for a mother board that I may not have needed in the first place, the PC had symptoms but not the symptoms it had after the repair shop decided to do a bios update which resulted in having to have a new mother board.
If he had put a new PSU in first that could have solved the problem we were having with the PC, without having to mess with the motherboard doing updates and causing a new problem . do I have any rights as to having to pay for motherboard? or is it down to the repair shop as they did update which caused a totally different problem to what I took it in for repair and resulted in having to have a new motherboard.. any advice much appreciated.