I'm wanting to buy a new multi-effects pedal, my current one is pretty basic.

Budget: £500

There's two I like the look of: the POD HD500x and the Roland GR-55GK w/ GK-3 pickups.

However I'm not very techy so any opinions would be really appreciated !

Thank you.
The GR55 is a better synth than a multifx. But it's a better multifx than an HD500 is a synth. You need to decide which is more important.
Thanks what I want is something relatively easy to use that I can plug my guitar into and create a wide range of sounds, i.e. distortion, clean, delay, wah, flanger etc. Also something I can take to gigs and just plug in and play.

I'm also open to suggestions for other pedals
Thanks I'll look into it. What's the difference between an effects pedal and a synth? Why would you want one?
An FX pedal modifies the tone of your guitar. A synth typically uses a special pickup that allows separate freq analysis of each string and then can map the note and dynamics into a synth that creates tones completely independent of your pickups. For example it may use sampled piano, sax, or flute waveforms as the playback sound.

Here is a clip in my profile that is using a GR55 to play a flute and an HD500 to play the wah flavored guitar tone over a 5 sec guitar looping (HD500 looper) some harmonics. Both the guitar and flute sounds are being generated at the same time from the same guitar using both the GK3 and the pups.

Secret Moment