During a few months of 2011, a work colleague who was seconded onto Thames Water, rode his bike from Horfield to Parkway, left it locked up and commuted via train
every day of the week!. I worked on the same job but commuted by train & taxi, stayed in the smoke (6 months in Southwark
Travelodge....

). Nothing happened to his bike but ironically, mine got nicked from the work bike shed back in 2014 during a break-in.
Here's Parkway:
They used to have sheltered bike storage but there's been building work going on so it's all changed. Frankly, I'd just get a bus or taxi. If you must lock it up, use two locks, remove saddle etc. Worth noting that insurance companies may specify a max time you are allowed to leave it unattended in public - I'm sure Cycleguard is about 12 hours.
Take the bus, Parkway is well serviced.