I went on the Walks Worldwide Corsica GR20 holiday in June/July 2010 (14 days).
The holiday was booked through Walks
Worldwide (offices in Ingleton, North Yorkshire and Hampshire).
The tour leader was Steve Stout (who may work for both Walks Worldwide and KE Travel, amongst others).
The walk was great; however, I cannot recommend the company or the leader for this trip; the words "touch" and "bargepole" come to mind.
Some of the alternative tour operators are:
Tour Aventure were the local operators for the trip, and it seems would accept direct independent bookings for even small groups.
tripadvisor.com has a posting (dated 11 March 2010) with negative comment on Walks Worldwide in a thread about a Petra trip (there are positive comments on tripadvisor about Walks Worldwide as well). The unflattering posting is dated 11 March 2010, and does not seem to be available in the "live" version of the thread on tripadvisor, but might be available through Google's cache, and is available as a pdf here (PDF, 85kb).
Walks Worldwide in Ingleton is part of a bigger group, Chameleon Worldwide (www.chameleonworldwidetravel.com), which is itself part owned (see press release) by Intrepid Travel (http://www.intrepidtravel.com/), so if you think you're supporting a small niche locally-based company (like I did), think again!
On my return, I e-mailed a full report/complaint. I had a swift reply back from Mike Wynne, Product and Operations Manager, Walks Worldwide
At the time of writing (8 September 2010), I have heard nothing more from the company (about a month after the supposed getting in touch) and seen nothing of the promised single supplement refund: promised much, but didn't deliver. In relation to the single supplement refund, I got fed up with waiting for it to be repaid, and donated out of my own pocket double the amount of the (not - yet? - refunded) single supplement to a local mountain rescue organisation (which is what I'd always intended doing with at least some of the compensation)..
When I booked the holiday, of the tour operators available, I opted to use Walks Worldwide as a local company and support the local economy: that was clearly a bad decision.
I haven't reported the full content of the complaint in detail here, as it is potentially still under discussion. However, to give an indication of one of the points in the complaint: the final night of the trip was in a hotel in Bastia (on this occasion, the Best Western). I had paid a single supplement for the trip (and made use of it on more than one occasion earlier in the trip). On the last day, on the arrival at the hotel in Bastia, the trek leader stated that he had no evidence that I had paid for a single room and was going to allocate me a shared room. In front of other clients and in the hotel foyer, I had to endure the embarassment of proving that I had paid the single supplement and back up my claim, and dig through my paperwork (which fortuantely I was able to produce) to prove my claim, to the apparent unwilling acceptance by the person concerned.
November 2016: as at 31 October 2016, Chameleon Worldwide Travel Limited ATOL 10186 has ceased trading. The company based in Alresford traded under the names Adventure Worldwide, Chameleon Worldwide, Families Worldwide, Schools Worldwide and Walks Worldwide and under the websites www.chameleonworldwide.co.uk, www.schoolsworldwide.co.uk, www.walksworldwide.com, www.adventureworldwide.co.uk and www.familiesworldwide.co.uk. See https://www.caa.co.uk/ATOL-Failures/Chameleon-Worldwide-Travel-limited/
Feb 2017: Walks Worldwide now appears to be part of the Natural Travel Collection http://www.thenaturaltravelcollection.com/: "Our portfolio now also includes Families Worldwide, which offers upmarket tailor-made and small group holidays for families - and the walking holiday specialist, Walks Worldwide, another brand originally created by Chris (and others) in the late 1990s."