Stuck seat post

The frame is a bianchi and the post is a Thomson. Due to some neglect and now a bit of growth I need to adjust the post. Which is well and truly jammed solid I have tried the hammer attempt from the side, on top to no joy and twisting in a vice except I ain't no the mountain. I've looked on here and seen talk about caustic soda this an option which comes with possible casualties me & bike. Any one know engineers or shops which can help for a small fee ?

https://www.facebook.com/theseatpostman1/

Check out this guy's channel - he's got a ton of videos dealing with various stuck seat posts / remedies.

https://www.youtube.com/user/shyflirt1/search?query=seatpost

Frame material & seatpost material?

Plusgas probably your best bet.

I've had plenty of success in the past but takes time.

https://www.facebook.com/thebikegeneral/

Frame steel post alu. Thanks I 'll have a look .

I finally got a Alu seatpost (wrapped in carbon) out of a steel frame using the caustic soda method (wish I had done this to start with). I managed to scrape out al of the carbon wrap that was left and the tube is totally clear however I can't seem to get the new post in more than a few cm. can anyone think of a reason - and I guess more importantly, a solution - for this? Im pretty sure it's the right size (27.2), it's a Tokyo fixed s-2 frame, I don't want to jam in and start the process again.

Have you greased it?

Yeah, I've tried to clean/oil the inside of the tube as thoroughly as poss after running the caustic soda/water through and the seatpost bolt is completely removed, still no luck.

28.6 v 27.2 nest measure both

Sorry I don't understand ?