TUI and Thomson before that hasn't used the BY flight code for several years they use TOM.
TUI don't add their flight code to outsourced flying as both Flybe and Volotea use their own codes regardless of the fact that they are operating on behalf of TUI.
It's Lolo Flights not Volo!
LoLo flights are using a EMB195 from Flybe for SOU to Skiathos from July to September 2018, it's a charter flight not a 'scheduled' flight, Kalamata was to be added from late September up until the end of the summer season but the flights never went on sale.
There hasn't been anything confirmed relating to the cancellation of the LoLo flight program for summer 2019, I should imagine that their planned frequencies have yet to have aircraft allocated but I have to admit it does sound a bit over ambitious, we're just have to wait and see!