[raggedyman2015]

i know there are several old threads about this but i was wondering what the costs were of the sender units for the tanks, are they the same for both sides ? do i need to replace them both?

i am in Northern Ireland and have a 2010 2wd 2.0 D Captiva

 

[Aussie Ed]

Cost...... readily stated on the internet. Price You can look up yourself.
Typically https://www.bestpartstore.co.uk/electrics/fuel-level-sensor/chevrolet/captiva/captiva-c100-c140

Both sides the same. No. If you have read the previous posts as you say you have on this Topic then you will have read that there is a primary sender combined with the pump and a secondary sender. Use the Advanced Search function to read fully. (acknowledgement to member Victor for this information).
Typically Fuel pump changed but still not working
Fuel gauge Issue
OPELFUEL SYSTEM - FUEL PUMP AND TANK GAUGE UNIT

Replace both..... probably best idea while you have access; unless you can verify only one is defective.

You dont say how you have established the sender unit is defective but it is worth noting that on older models, poor earth connection is a primary issue to investigate.