Exactly, it probably would be to let a small bank go bust.
Remember the reason that RBS and others got a full bailout last time was because their potential collapse was seen as an existential threat to the proper functioning of the domestic economy. A small bank wouldn’t be regarded that way.
In addition to being authorised as an e-money institution, Dozens are also authorised as an investment firm. For this reason I believe Dozens would claim money held with them is better safeguarded than money held with a pure e-money firm
Also, now retail banks are distinct separate entities from their parent companies and investment arms, the collapse of which (the latter two) would undoubtedly cause harm to the UK.
HSBC UK’s collapse (for example) is much easier to allow than that of HSBC plc.