Business visa validity after I switch organization

You should not try to enter UK with your current visa and instead re-apply with an application reflecting your changed circumstances (i.e. change of employer).

Source: comment by expert user @GayotFow to your Q:

[...] What you have described is a material change of circumstances and that falls as mandatory grounds under Paragraph 320. So if you get caught, expect big time trouble, up to and including removal.

That basically sums it up nicely. If you want to know more, this is a material change of circumstances in the sense of paragraph 321(ii)

321. A person seeking leave to enter the United Kingdom who holds an entry clearance which was duly issued to him and is still current may be refused leave to enter only where the Immigration Officer is satisfied that:
     [...]
     (ii) a change of circumstances since it was issued has removed the basis of the holder’s claim to admission, except where the change of circumstances amounts solely to the person becoming over age for entry in one of the categories contained in paragraphs 296-316 of these Rules since the issue of the entry clearance; [...]

in addition to paragraph 320(7A) False representation, false documents and/or non disclosure of material facts:

Your refusal notice could look something like here in the guidance for paragraph 320(7A) here on page 12:

Failure to disclose material fact In your application, [you or another person] failed to disclose the following facts
[state facts].
I am satisfied that these facts were material to the application because
[state reasons].
Appeal rights depend on category application

You should note that because this application for entry clearance has been refused under paragraph 320 (7A) of the Immigration Rules, any future applications may also be refused under paragraph 320 (7B) of the Immigration Rules.

A refusal under paragraph 320 (7B) of the Immigration Rules attracts an automatic refusal period of up to 10 years. The period starts from the date of the previous event in which the deception or submission of falsified documents or information was employed.