Bob: I've been on over a dozen Trav Dept tours, most of which were very good, great value for money and have had plenty of singles on them (14 on one!). Always got a twin or double for single use. The Irish couples are always friendly and good 'craic' as we Irish say. The only exception was a Texas trip a few years ago on which we had an incompetent TM and a hotel on the itinerary we received was changed to one 20 miles N of Dallas instead of downtown. I have heard from a couple of people that their solo friendly are mostly singles and maybe 2/3 women together as you get on JY trips.
Sylvia: I go with them from Dublin and have usually flown Aer Lingus to Europe. They rarely use Ryan Air from Dublin and use other airlines besides BA from there for long haul. Going from Dublin for me cuts out an airfare to the UK and maybe 1/2 hotel stopovers. Trav Dept is limited from the UK but plenty of choice from Dublin.
On the subject of TMs, had one mediocre one with JY in the past and on the same trip one of the local guides wasn't great either. Went with Solos once. That trip was badly researched and the TM was like a sergeant major. Had the same fantastic TM on 2 One Trav trips to Asia recently.
I remember on my first JY Cuba Tours over half of the hotels were awful, with most of the group asking for changes throughout the tour. I did pity poor Leigh Britton who was a fab TM (must mention Feli who was the best and nicest local guide ever). Luckily I did a couple more JY ones where the hotels were OK tho some too far out, as you get with most companies.
My gripe is that the well known UK singles companies are getting very expensive and like Jenny (aka Crystalbling) I like to travel. I wouldn't mind dropping a * for hotels - Trav Dept sometimes gives you a choice.