I advise on the assumption that you have entered inot a contract of sale rather than an HP agreement.
The Printer:
Reject the goods and claim a refund. You can choose to have it repaired if you so wish, but since it doesn't seem to be a very good printer, personally, I'd choose to take the refund. Your statutory rights to demand the refund/repair/replacement is under the Sale of Goods Act 1979 (Section 14 (2B)(a)). You are quite right that the printer should be fit for purpose. It isn't, so you can reject the goods and claim a refund.
If you don't get anywhere you can raise a small claims action at your local sheriff or magistrates court. Alternatively, if you paid more than 100 pounds for the goods using your credit card, the creditor (the credit card company) are held to be jointly and severally liable under Section 75 of the Consumer Credit act 1974. So you can aske them for the refund, and if they give you the runaround, then your small claims action can be against them, the seller, or both. In my experience I stop getting the runaround when the court summons is received.
The Fridge Freezer:
Same rights, same Act (SOGA 1979), slightly different section. Reject the goods under Section 14 (2B)(e) - the goods should be 'durable' to meet the test of being of satisfactory quality. Most reasonable people would expect a fridge freezer to last substantially longer than 18 months. You are also entitled to claim for consequential damages for the sellers breach of contract (the fridge not meeting the implied standard of satisfactory quality). This means they not only owe you a refund, but also a refund on the cost of the earlier repair . I can't believe they charged you for a repair to an appliance that should never have broken down in such a short time!! Again, if you paid for the goods with your credit card S75 of the CCA1974 kicks in.