Disclaimer: double check with a practicing attorney in the UK, in the event that things have changed or were transcribed differently (if at all) in the UK law (my French IP law is a bit rusty).
To cut the very long story short, your "All IP belongs to the company" section, while perfectly legal (and enforced) in the US, might be completely void in the UK.
The European Union passed the copyright directive in 2001. A directive is a law framework, which obligates individual EU member States to write laws in a reasonable period of time (some drag their feet) that share agreed upon standards and practices on the matter that it regulates (in this case, copyright, intellectual property, patents and digital rights management).
I've absolutely no idea if/when it was transcribed in the UK, which is your country based on your profile.
Among the colorful things that the directive says, is that you cannot forgo the copyright/ownership of your creative work, be it a newspaper article, a book, music, video, software code or otherwise. You read that right: cannot, even if you want to and sign an agreement that you do. It is unalienable.
You can only do the next best thing, which is to grant exclusive rights on your work to your agent, employer, customer, etc.
Depending on whether your employer consulted an IP attorney or not to draft generic work contracts, you might very well be in a situation where you're granting "ownership" rather than "exclusive rights". In France such a work contract clause would get dismissed in most courts as invalid.
Which is not to say that you should taunt your employer or not document what he finds acceptable with him to avoid future problems. But keep the point in mind as a joker in case your relations degrade.