Mrss, Alice, mummyina, and everyone else, the odds really are in your favour. Seriously, the change in the grammar exams process, now means most people who passed will have an offer, about 500 got through to 2nd stage and there are about 400 places. This has a knock on effect on those who really want indies.
So majority of DSs didn't make it to the 2nd round of grammar exams. This is probably one of the reasons why W & T have had 'more applicants than usual' this year ( as well as it being a bulge year). Assuming they haven't invited more people than usual for interviews ( which I don't think they have done), then once you've made it this far the odds are definitely in your favour Also there shouldn't be that many people who didn't get into grammars now needing the indie back-up. If this makes sense.
I believe last year we figured the odds of getting a place at T & W, after interview is something like 2/3. Then considering if you sat both schools you can only take up one offer, the odds start to get better for those waitlisted. Even though they do over offer.
Hopefully, you will be the ones posting this next year! All the best. 3 more sleeps.