Screwed for Cambridge application?

Want to apply to Cambridge for engineering and I really do want to get in. Predicted grades will (with fingers MASSIVELY crossed) be on my side as 4A*, incl. maths, FM, physics. Extra/supercurriculars not so much. No competitions. I'm going to read a lot of books and do a lot of personal mini projects over the summer but I don't know what else to do to make myself stand out. Sounds like everyone else has done so much and now I'm really stressed.
Also my problem solving skills are absolute *******e. A level maths questions are doable, even if the harder ones need going over. Anything beyond that and I'm terrible. I did a past NSAA paper (because that's what the ESAT will be like) and I scraped a 4 - admittedly I think that will come with practice. But I mean problem solving in terms of the type of stuff I might be asked in my interview, I'm pretty bad at that. Are there any other places in which good problem solving skills will even be relevant, though?
Anyhow, I just generally feel like I will be lost in the sea of applicants who have good grades but are crap otherwise lol. Any advice would be appreciated.

Have you looked at the Isaac Physics website? It's got hundreds of maths/physics problems and you can gradually work your way up in difficulty from the practice questions to the challenge ones (some quite similar to what you'd get in the NSAA). Found it helped my problem solving quite a bit

Have you looked at the Isaac Physics website? It's got hundreds of maths/physics problems and you can gradually work your way up in difficulty from the practice questions to the challenge ones (some quite similar to what you'd get in the NSAA). Found it helped my problem solving quite a bit