1. UK banks will not ask for massive costs for receiving money. You might lose a couple of percent in the exchange rate and, if you try to bank a foreign cheque or draft, you might also be charged £10 or £15. What are the "massive" costs that you mention?
2. If you receive an inheritance, then there may be inheritance tax to pay by the estate of the person leaving you the money but if similar taxes have been paid in another country, the chances are that there will be no more to pay. The UK has "double taxation" agreements with a lot of countries.
3. ISA are not just for English people. There are lots of other nationalities in the UK who have ISAs but you must be resident here and paying income tax to open one. The limit is £15k this year.
4. You can only open one new cash ISA each year. You can transfer last year's ISA around as much as you like if the providers will let you, but you can only open one new cash ISA this year with up to £15k.
5. There are lots of ISA provides. You pay your money and take your choice. The "money" tab at the top of this page might help with decisions.
6. Instant access ISAs give low interest and instant access. Fixed rate ISAs give higher interest but the money is invested for a fixed term.
7. All ISAs are an investment. If you expect to be paying UK income tax for the next few years, it would probably be worthwhile to put some money into an ISA. Stocks and Shares ISAs are more risky than cash ISAs but they offer the potential for capital gains as well as income.
8. If you are not used to investing, you should expect someone, at some stage, to tell you that you need to put all your money into xxxxxxx because it is the hottest investment and you cannot lose - high returns are guaranteed. Any such advice should be ignored.