Want to Help Fledging Blue Tits (1 Viewer)

Hi, just wondered if anyone could provide advice which would be really appreciated. I have a bird box which I inherited when I moved into my house (which is a terraced house with a small back yard). This year we were lucky enough to have blue tits nesting in the box and 2 fledged on Friday. It was extremely stressful as the weather was horrendous. There isn't really anywhere in our back yard for fledglings to seek cover, shelter and hide from predators, plus they are tweeting for their mother a lot which brings unwanted attention to them. After a terrible cold and rainy night (typically the worst I've seen in a long time) I searched our yard high and low and could not find the 2 fledglings. Having read that it takes at least a couple of days for birds to develop and learn to fly, I fear the worst that a predator has taken them. We never see cats around, however I did see bigger birds hanging around when the fledglings were in the yard. The mother returned on the Saturday with food and was calling out and searching but clearly could not find them. Since Saturday lunch time the mother has not returned.

I really want to prepare in case we are lucky enough for them to nest again. Does anyone have any advice on how to what to add to my back yard in order to help - perhaps some potted plants on the ground to provide shelter, if so which plants would be appropriate? I just want to help them as much as possible to be successful and provide a safe environment and shelter. The mother did such a good job, it was heartbreaking that struggled once they left the nest and I feel I should have done more. Any ideas would be appreciated. Many Thanks