Postdoc salary negotiation (UK)
This depends heavily on the funding source. For all UK funded postdocs the pay will be set on the national scale - current rates without London weighting are up-to-date, but I'm not sure if the comments about the London weighting are correct.

For research council funded postdocs I would expect the salary range to be fixed somewhere between spine point 27 and 40, with the initial upper limit more likely around spine point 34. This is close to the numbers you quote. I would not expect much flexibility unless they can find additional funds to supplement the (fixed) funding from the grant.

On the salary increase in post: there would typically be a 1 (one!) spine point increment after the second year. I'd be very surprised if a substantial increase along the lines you're wanting could be negotiated, let alone after the first year.

If the funding is not pure research council then there may be more flexibility.

As someone who's been on both sides: I have fielded salary questions, particularly from overseas candidates, and (done sensitively) I don't think it will be held against you. The above is more a warning that the constraints of RCUK funding may make it impossible to get a solution that's acceptable to you.