Here are the corrections for the passage with the identified errors:

1. **Line 1:** Change **"or in"** to **"or on"**
**Correction:** "Most British people go abroad on holiday to visit family, or on"

2. **Line 3:** Change **"leave"** to **"leaving"**
**Correction:** "to get urgent treatment before leaving the UK."

3. **Line 4:** Change **"forms"** to **"form"**
**Correction:** "They have to get a form which explains"

4. **Line 5:** Change **"if they fall ill or"** to **"if they fall ill,"**
**Correction:** "they should do if they fall ill,"

5. **Line 6:** Change **"have"** to **"has"**
**Correction:** "and what arrangements exist in each country for medical treatment."

6. **Line 7:** Change **"simply"** to **"simple"**
**Correction:** "The regulations are fairly simple; but if people do not"

7. **Line 7:** Change **"have"** to **"has"**
**Correction:** "do not have this information, they may find"

8. **Line 8:** Change **"care is"** to **"care to be"**
**Correction:** "they may find that private medical care to be extremely expensive."

9. **Line 9:** Change **"is"** to **"can be"**
**Correction:** "It can be not unusual for people to discover that"

10. **Line 10:** Change **"many"** to **"more"**
**Correction:** "becomes even more complicated."

Here’s the revised paragraph with corrections applied:

"Most British people go abroad on holiday to visit family, or on short business trips. People are advised to find out when to get urgent treatment before leaving the UK. They have to get a form which explains what they should do if they fall ill, and what arrangements exist in each country for medical treatment. The regulations are fairly simple; but if people do not have this information, they may find that private medical care can be extremely expensive. It is not unusual for people to discover that they do not have enough money with them to pay the total costs, and in so circumstances an already difficult situation becomes even more complicated."