My employment contract explicitly refers to an employee handbook for a number of issues, using the phraseology “see employee handbook”. My employer (a small company) never created an employee handbook for review (and only created a contract for review after four months of employment) does this mean that some or all of my employment contract is invalid? For instance if I was to leave without fulfilling my notice period or did not adhere to a ‘non compete’ aspect, is it likely that UK employment law would favour my employer?
If you want to get advice specific to your situation, the Citizen's Advice Bureau would be the place to go in the UK.
Broadly speaking, the fact that an employment contract refers to a non-existent employee handbook in one section has no impact on other sections. If there is a section in the employment contract that talks about the dress code and refers to the employee handbook for grooming standards, that has no impact on a section in the contract that refers to your expected notice period. If that section of the contract is clear, you'd need to serve whatever notice period you agreed to. On the other hand, if the employment contract's section on the notice period says solely to see the employee handbook and no such handbook exists, you could make a reasonable argument that you should default to the statutory minimum of a week and that the employer can't force you to give more notice than that.
Assuming that your company did what small companies commonly do and went out to a grab someone's employment agreement template rather than drafting their own, I would expect that most of the "see employee handbook" items would be for more minor/ ephemeral issues like grooming standards rather than more core issues like notice periods and non-compete agreements. It would be weird for there to be a non-compete agreement that wasn't part of the employment contract or a separate non-compete agreement. It would be weird for the company to have to issue a new employment agreement when they update their dress code to allow business casual attire on a Friday. I would expect that notice periods would be spelled out clearly enough in the employment agreement to be binding. But that obviously depends on the specific agreement you and your employer signed.
For instance if I was to leave without fulfilling my notice period or did not adhere to a ‘non compete’ aspect, is it likely that UK employment law would favour my employer?
If those sections in your contract say something like "Details of the non-compete rules are in the employee handbook", and that handbook does not exist (or was never shared with you), then they would be unlikely to take any action against you for "breaking" them.
If the details are laid out in your contract, but some other unrelated section like dress code says "See the employee handbook" then you are still bound by the terms that are in the contact you signed. However, if you ever got a formal warning for dressing inappropriately , you cold argue against that on the basis that they never defined "appropriately".