Williams faces 'a lot of work' to close on Ferrari/Mercedes in 2016

Valtteri Bottas's fifth place in the Brazilian Grand Prix put third out of reach of Red Bull and ensured Williams finished in that position for the second successive year.

While there was euphoria when Williams achieved the feat in 2014, having finished ninth the previous year, celebrations were more muted this time, after a season in which it had hoped to get closer to the front.

"It's a bit different to the feelings last year, but it's great," deputy team principal Williams told Autosport.

"It's great to get third for the team, everyone's put so much effort in and to consolidate our position is a really positive step.

"But it's all about looking ahead to next year, we've got a lot of work to do to achieve what we want to achieve."

Williams has generally been the third quickest team this season but struggled operationally at times, particularly during pitstops.

In order to make the next step and fight at the front more consistently, Williams said the team must improve across the board.

"I think we have to work across the whole of the team," she said.

"There are areas across track operations we know we need to do a bit better at, we need to do a good job in the tunnel and then in every area.

"If you're going to change and move upwards, you have to change and look at every area across the whole team in order to achieve that."

Both Bottas and team-mate Felipe Massa have performed consistently over the course of the season - and Williams believes that has been crucial to the team's success.

"They've been fantastic," she said. "I don't think you could fault either Valtteri or Felipe this year for what they've done for the team and we look forward to seeing what they can deliver next year."

Williams halted development of this year's car early for focus fully on 2016, with the last upgrades on the FW37 understood to have been fitted at the Singapore GP in September.