Modal verbs to express ability

I was so worried that I couldn't sleep / couldn't have slept and I lay awake all night.

Although the shop was very crowded, we could / were able to get the shopping done quite quickly.

We hope you’ll be able to offer us a discount if we stay in the hotel for two weeks.

A lot of unique markets could be found in London.

I’m really pleased to hear that you could come to visit me next month.

I can’t carry everything, so I had to leave some things behind.

I was very happy that I could meet all your friends when I visited you last month.

Even though we were cold and tired, we could / were able to reach the top of the mountain.

I could buy / could have bought my tablet more cheaply online, but I got it from my nearest independent computer shop instead because I like to support local businesses.

I ______ (not) come shopping with you tomorrow – I’ve got a dental appointment.

Can you / Are you able to hear the neighbours’ television? It’s far too loud!

When I was a small child, I could / was able to sing beautifully, but my voice isn’t so good now.

It would be much easier if we can find the information on the internet.

We could find our way around Rome easily by using online maps on our smartphones.

I’d be grateful if you can advise me about which book to buy.