Technically no dart frogs need UVB or even heat unless you live in an area where it gets under 20 or so degrees. I personally provide it since I still believe it has benefits. I would definitely have an LED light for the plants and it looks better.Do any of these species need UVA/B as my current epidobates tricolour do not (I have an led light and a heat pad.
I use the arcadia shadedweller which is 6% UVB which is the highest amount of UVB that I would give darts. I recommend the arcadia jungle dawn for LED lights and honestly anything else from arcadia which I believe is quite common in England. If you provide UVB make sure there are lots of hiding spaces or bushy plants to maintain cover for the frogs should they want to get away from the light. If you don't get a UVB light make sure your supplement for your fruit flies has vit D3.
Dart frog care is essentially the same no matter the species so it isn't too far off from your E tricolour. since you have an exoterra I also recommend putting seran wrap over some of the mesh lid to help with humidity