Hi Nisha,
Often larger companies have dedicated applications for work experience. You might have missed some of the application stages as they usually open around December - January.
Aerospace work experience is tough due to the strict security restrictions, but you might be able to get similar insights at companies such as Renishaw (Not too far from Bristol), who deal with manufacturing technologies. I can personally vouch for Renishaw, as they did a fantastic weeks placement, but not sure if they are still open for applications.
Last year, I tried several aerospace companies, and was shot down by all of them due to either security restrictions or due to a lack of interest from the companies.
Most importantly, work experience in any sector of engineering is better than nothing, so don't just restrict yourself to Aerospace. Take a look at manufacturing, electronics, etc. Companies like Ultra PCS are doing work experience in Summer, other organisations like BAE Systems, Thales, Airbus, or Babcock may have opportunities too.
I'd suggest having a browse around and seeing what opportunities interest you. If you really want to, you can always travel out and get a hotel to be able to visit a company further away. Cold emailing can sometimes work, but I've found it has a low success rate.
Hope this helps