Those types of schemes are in the 'nice to have' category. Good to do if you can spare the cash without damaging your other savings plans. You don't want to be relying on any single concentrated holding, let alone your own employer, as a way to save sustainably. I can vouch from personal experience of what happens when it goes wrong.
Lovejoy: When investing relatively small amounts, you need to look to absolutely minimise fees and trading costs. It's also probably not worth investing in individual shares and you should focus instead on platforms which can offer various funds and trusts (eg Fidelity) or a DIY portfolio from the likes of Nutmeg. Make sure you are investing via an ISA wrapper- don't worry if you are also investing in a cash ISA, you can save in more than one as long as you don't go over your allowance in aggregate.