Yes you can.
What you have to do is take off all relevant expenses from your GROSS pay for this second job which will leave you with a net profit/loss. Do the same for your training course supply business. Add both net profit/losses to your total GROSS pay from your main job and this will give you a total income figure. Take your personal allowance off of this and then calculate the tax payable on this figure. Finally when you have a total tax payable figure, deduct the tax you have already paid during the year (ie the PAYE incurred in both of your jobs). This will leave you with either a refund due or some tax to pay.
Hope this helps!