Snap-on tools IMHO are very good but over-priced. There are other companies that produce tools of sufficient quality for aircraft use.
Halfords Pro tools are actually quite good and are a bit under-rated. I think they still come with a lifetime warranty.
I personally have a mix of Halford Pro, Kennedy (from Cromwell), Snap-on, Bluepoint.
As for the cable tie gun... Unless you are working in loom manufacture or rewiring huge runs of cables, the extra price versus the effort saving doesn't seem worth it. If you are determined to get one, then Ebay or Cromwell tools are your best bet.