Fontella, I feel your pain regarding the mice I have had these every year for 7 years. I will try some of things you have done. I’m glad you are finally rid! I have been bidding on properties as I do pay the bedroom tax but this new house is more expensive £40 a month which is a lot as a ft student.
I am too scared to say I am 'finally rid' as they have been so persistent over the years and have made my life an absolutely misery as I am petrified of them to the point of phobia. I once stayed a whole weekend upstairs in my bedroom because I saw one in the lounge and was too scared to go back downstairs.
Eventually however I heard a scratching noise upstairs and one shot across my bedroom floor. That was it! War was declared. Up until then I'd only put down humane traps (never caught a thing) so it was snap traps (also never caught a thing) scrupulous hygiene, sweeping, wiping away all food scraps, wrappings etc. (if there's no food for them to eat your home becomes a lot less attractive) moved kitchen bin to outside cupboard, used all the various repellents and sprays and the peppermint oil (did no good as far as I could tell) - it was only blocking off those holes under the kitchen units, plugging in the repellant thing and cutting away the shrub that was near the window and they seem to have buggered off.
I did call in the council mouse man at one point but he said he couldn't see any evidence of 'infestation'. He found one mouse turd and said if I was infested there would be a lot more evidence of them, so he declined to put down the poison and refunded my money, even though I was regularly seeing mouse/mice. I'd walk in my kitchen and it would be running across the worktop! I also once was sat talking on the phone in my kitchen and one of the fuckers ran out from under the cooker, I screamed and it shot back in again! I was a nervous bloody wreck.
It was the pest bloke from the council who suggested cutting back the shrub from the window as apparently they can and do climb into houses that way.
The idea is to make your house as unattractive to rodents as possible and that's (supposedly) how the plug in thing works - through the noise and the electrical current which they can hear/feel. Whether it works or not I honestly don't know but along with the other two things I mentioned - it appears to have worked for me, but I don't want to say they are gone forever ... because I'm terrified they will come back. All I can say is it is seemingly working for now.
I do sympathise with you though - it is hell, and I wish you luck in getting rid!