Luckily I managed to avoid that yesterday, but good advice from Bracknell, I hope she told you to get a 90 (although that serves the main road rather than the bus station itself), 285 or 490 (not a H25 as it goes round the houses).
Kew Bridge is also about a 10 min walk or short bus ride from Gunnersbury, so is a good option if an incident via Richmond happens again.
The 90 and 285 in that direction share the same outside stop, while the 490 traverses the whole bus station, and the outside stop is almost certainly quicker. There is no need to cross the road. The 90 and 285 have also switched to double deckers in the last 2 months.
But yes, there are a lot of alternative options along the whole route:
Hounslow to Hounslow Central (15 minute walk or use the H20 from further down the road).
Brentford to Boston Manor (20 minute walk or use the 195/E8).
Brentford to Ealing Broadway (use the E8).
Kew Bridge to Ealing Broadway (use the 65).
Chiswick to Turnham Green (use the E3).
Barnes Bridge to Hammersmith (use the 209/419).
Barnes to Hammersmith (use the 33/72).
Putney to East Putney (6 minute walk, and an official out-of-station interchange).