Please dont try to remove the back clips, they need to remain fixed because when the bracket is placed against the facia board there will be no room to refit them and it is not necessary for them to be removed.
Remove ONLY the front clips by using your finger strength only. DONT use tools.
How...
Yes. Just remove the front two clips. push the gutter up into the back clips, refit the front clips, job done. Have done this many times as the weathers seals(strips of rubber) fail after a while and you get drips.
Gutter should follow a standard. I think you will find that Wickes gutter does...
The clips are not integral and you should remove them before trying to fit the gutter. then push the clips one at time down and into the bracket.
Try to practice before you slip the gutter in and you see how easy it is. Do this before you mount the ladder, pull off and push on.
Hopefully thats...