Paco, reason he talked 100hrs was the no requirement for dual received by EASA FI for PPL flight test.
Also with 100hrs on type (light singles) he'd not need whole TR course, just flight test - can be combined with PPL. In reality he'd do some prep training, but could then be less restricted with TR courses as such.
For recreational flying only and in the UK, despite having my preferences to KEEP OUT, I can only concur it's most sensible doing your training in the UK.
If you want it fast, can be done over summer, with least disruptions due to weather, especially if working fulltime.
If you want to combine training with fun trip/holiday for your lady, to make any sort of financial advantage for PPL or so only, Canada would be second choice compared to US. You can still find hilly place/school, but in reality, you'd not going to do too much of off-airports and pinnacles in most places during initial training.
Also, the USD vs other currencies isn't great, but still better than Canadian dollar. those rates are nearer UK dual rates incl VAT than average US cost.
Again, for short time and only private flying, you'd end up spending more, by the time you're proficient for safe solo flying, especially if you're most likely to rent R22 and as you say, prefer not to use that for PPL or most of it. You only see the bigger picture when flying R22 from left seat, the margin for error in some maneuvres, what you'd not see as student.
With reasonable availability of Cabri at UK schools, I'd recommend it. It's lot safer, stable, reliable and plenty passive safety/crashworthiness built in and handling preventing the need. One can't compare R22 with Cabri, trying to draw too many equivalencies, other than being helicopter and the engine used.
As once a year flyer and PPL only, you'd lose proficiency faster and I assume you may not entertain too much currency flying after long break (hey, TR valid, so legal to fly, attitude possibly). Cabri would help being docile and safer, plus for trips, the luggage space, endurance, comfort, cyclic trim, it'd all be advantage compared to R22.