I could’t find much about your equipment… I couldn’t find anything on the Maplin.
Noise is an analog problem. Hiss is usually from the preamp (the preamp built into your mixer in this case), although it can also be acoustic/ambient. The trick is to use low-noise equipment in a low-noise environment and then try to get a good strong signal for a good signal-to-noise ratio. Solo acoustic instruments (and vocals) can be the most difficult things to record!
Noise reduction isn’t perfect. So even with the latest pro software, pros still record in soundproof studios with very good low-noise equipment.
Any good performance/studio microphone is going to be low-impedance balanced (3-wire) with an XLR connector. And of course, the mixer or audio interface needs matching inputs. (Your Phillips mic and the mixer appear to be high impedance unbalanced.)
I’m flitting between plugin mic straight into computer…
The line-input on a soundcard is often acceptable, and you can plug a mixer into it.
The microphone input on a regular soundcard is high-impedance unbalanced, so it’s the wrong match for any good microphone, and the built-in preamp is usually noisy and poor quality making the mic input on a soundcard or laptop worthless for quality recording.
If you have a laptop with no line-in, you generally need a [u]USB Audio Interface[/u]. You can also find mixers with USB outputs. Even with a desktop computer, an audio interface is the standard way of doing it. (These devices bypass your soundcard.)
Another option is a “Studio Style” USB condenser (AKA “[u]Podcast Mic[/u]”). These are super convenient, and they are economical since you are essentially getting the USB audio interface free with the mic. (These usually run $100 - $200 USD). The downsides to a USB mic are that you can generally only use one at a time (no stereo or multi-tracking) and you can’t use them with a mixer. And, many of them don’t have a gain control which means it can be difficult to optimize the signal-to-noise ratio.
Acoustic guitar is most-often recorded with a studio condenser microphone. in fact, almost everything in “the studio” is recorded with a “Large Diaphragm Condenser”. Condenser mics tend to have better high frequency response for more “clarity” or “sparkle” than a dynamic mic. You can use a more mellow sounding dynamic mic and add some high-end boost, but boosting the high frequencies will also boost the hiss.
Studio condensers require phantom power. Almost all audio interfaces with XLR connectors can provide phantom power and many mixers can too. Most stage/performance condensers use a battery. (Dynamic mics don’t need power.)
…A good recording all starts with a good performance on a good instrument in a good quiet room (either a “dead studio” or a “music room” with good natural reverb), picked-up through a good mic with good mic positioning, and a good (quiet) preamp.