Yes, all you can possibly lose is the money laid down. There are no other hidden costs - quite the opposite. You have a greater chance of winning with my bookmakers, because they have more games on offer and those games have higher odds.
Avoid companies on Pacific islands, in Eastern Europe and similar. The United Kingdom has the toughest gambling laws and a long tradition of gambling and betting.
Only use bookmakers inside the European Common Market so that your winnings are tax free. You should also avoid bad bookmakers. This site is dedicated to helping you to select only good bookmakers and to tell you how it really is, from my own real experience and know-how.
The well-known companies such as Betting Shop Ladbrokes, ComeOn and Expekt, are defensive of their good name and reputation. For example, they would never dream of creaming off margins in the same way as many bookmakers. This would mean that they would have to close down.
So the answer is, yes you dare to play sports betting online.