Easy answer - go flying with an instructor for an hour or two before your test!
All of us suffer skills degradation when we don't fly for an extended period. There are times when it's not really an issue, and there are other times when it is an issue. I haven't flown for a month due to the weather, I'm supposed to take my sister flying on Sunday (weather permitting), so I'm planning on spending an hour in the circuit on Saturday first - it's not essential, but I'd feel more comfortable with it. Likewise, if you have a flight coming up which you don't feel comfortable with due to lack of practice, then the only answer is to get up there and practice first.
Good luck with the skills test!
FFF
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(PS - I hope you're not wasting your 3-hour round trips! Every airfield is different, but I know if I go to the airfield and don't fly, it's never wasted. I can always find something to do or someone to talk to - either chat to an instructor about something that's bothering you, or talk to other pilots about flying, or just socialise. But don't just go there, look at the TAF and then go home!)