Two sides of A4 maximum using a clear font (personally I like Open Sans but anything like Calibri or Arial would be fine) at a legible size (so I'd go no smaller than 10 and probably 11 or 12) for your text. My style usually has my name and contact information at the top of the page, then a couple of sentences highlight some key features from my experience that match the person and job spec (so if I was applying for a job as a delivery driver I might say something like "I have held a driving licence for over x years and have never had any motoring convictions or accidents during that time") followed by my work history. Next to each entry I'd put some information about what experiences and skills the job either gave me or allowed me to demonstrate (tailored to the job you're applying for).
I tend to put slightly more detail about more recent jobs than older once (unless there was something from an older job that was very relevant). So when I was last doing my CV I had done some work experience with the local Council only a few years prior to writing but as that was only three weeks and not directly relevant it tended to be a one line entry such as "Data Entry Clerk - Worked for three weeks inputting data from paper surveys onto a database. This required me to demonstrate the ability to complete a repetitive task whilst maintaining a high level of accuracy". Whereas the job I was actually doing at the time I wrote a short paragraph highlighting things I'd achieved, skills I'd developed, etc etc. I've put my education stuff down with a couple of sentences about things my degree gave me/demonstrated and then just a line for A-Levels and GCSEs ("I have A-Levels in X, Y, Z and 9 GCSEs at A* - C including English and Maths"). To be honest though I might not even bother at this stage to include anything other than my degree but certainly I've not put more detail than that even when I was first writing my CV.
Then it's just any other odds and sods that are relevant so I usually thrown in a line about my driving licence and access to my own car, familiarity with computers and things like Microsoft Office (though that's probably given these days!), if I've currently got a First Aid certificate I'll chuck that out. I thrown in some other certifications that I hold if they're relevant to the job I'm applying for at that stage. And then at the very end if there is room a sentence on hobbies (which are at least vaguely interesting rather than just "watch TV"!).
I also don't bother listing my references on my CV and just put a note at the end saying "References available on request".
Then if required a covering letter one side only (unless they ask for more!) highlighting some key features about me and my experiences that match the person spec and job description.
That seems to have worked so far! But CV writing is more of an art than an exact science I think!! Personally I'd never pay money for someone to write my CV for me. You'd be far better served using the suggestions of the people on this thread and having a Google around and finding examples of other people's CVs. Put it together and then ask a friend or family member or two to go over it.
The other thing I'd say is not to sweat too much effort into your CV as you'll find that a great many jobs these days (certainly for larger firms and even smaller ones) will have application forms that you fill in that capture everything you'd put into a CV anyway. Some I know love to make you upload a CV and then complete an application form anyway but I assume those firms are just sadists so you probably don't want to work there anyway