I'm not in the UK, but I have been a grad student for a while now.
I think it's perfectly acceptable to call and inquire.
Most PIs I know get a zillion emails a day with applicants and a few fall between the cracks.
No one has ever been upset with me for calling - responses ranged between "Yes, I noticed your email but I am swamped right now I will contact you in X time." and "Oh, I hadn't even noticed your email! Good thing you called. Can you tell me a little about yourself?/I'm sorry we're not looking for more lab workers right now".
I would wait a few more days.
But you didn't apply to the job you want that you're trying to contact this person about - you applied to a different job. So it's likely that your resume has ended up in a different pile. Re-jig it so it's appropriate for the job you want, rewrite an application letter and send it in.
Pod. I don't know how your university's application system works, but I know that, at my university, it's all online only AND for every position in which you are interested in being considered, you have to submit a separate application. HR is very strict about this process.
Also, I have had an applicant contact us and say, "Well, I applied for this job a few days ago, and no one has contacted me yet so I'm calling to schedule my interview." I had to repeatedly tell this person (with a doctoral degree, no less!) that WE will contact her to schedule an interview once WE determined she was qualified for the position. She had just graduated and just couldn't understand why I wouldn't schedule her for an interview because SHE wanted it -- I'm thinking this isn't someone who spent any time in the working world. I'm also thinking she didn't have the practical experience we needed, like a residency or equivalent inpatient experience, because she wasn't contacted (if she had a residency, she would've had to undergo an application and interview process like getting hired for any job so I conclude she bypassed that).
Anyway, as someone who reviews applications and resumes all the time, it's kind of annoying to be told that the person applied under a different position so go find it there. I had to go through 62 online applications the other day and forward them to the relevant parties. The last thing I'm going to want to do is search for some applicant's resume because the applicant doesn't want to take the step of reattaching it and sending it again for a different position. I know it sounds like the applicant would be inundating the company with resumes, but I think it would make it easier for the hiring manager to find it.
Side note -- if you only have to e-mail your cover letter and CV, a meaningful subject line and meaningful file names are fantastic "minor" details. To me, it really shows organization and attention to detail (and makes it a lot easier to find someone's e-mail or for what position that person is applying). Something like this:
Subject: Job #XXXXXX -- Postdoc Researcher
Attachments: PostdocResearcher_CoverLetter_Redcat_102312.doc and PostdocResearcher_CV_Redcat_102312.doc
I often open the resume attachment and find all sorts of weird filenames and even cover letters that are for a different position.