This is excessive and not required.
A gas safety check is not required if you have 1 disconnected the gas bottles from the supply, and 2 do not have mains \ natural gas to the property (as there isnt a risk gas may still be connected and enter the property).
If I was you, I would call a local plumber and get them to cap off the empty pipe (you dont need a gas safe certification), and its about 20 minutes work, so shouldnt cost you more than £60 (£80 if in the greater london area).
Please let me know if you have any follow up questions.
If you call Calor up they will often come and collect the bottles from you free of charge, or put them on ebay and you will probably get the £60 plumbing cost back in selling the bottless).