You can use the term, but you cannot trademark it and even adding the ™ will afford no protection. Similarly, it is not possible to trademark other similar terms such as 'Limo Agent', 'Limo Sales', 'Limo Hire', 'Limo Services', 'Limo Firm' and so on. Why? Because these are everyday, descriptive terms and used to describe a service. The law cannot and will not allow the trade marking of such terms, otherwise the provider of that service would have an unfair advantage over his competitors.
Similarly, you cannot trademark a generic terms, which would describe the general category to which the service or product belongs. For example the word "Limousine" or "Limo" is a generic term for limousine, thus it is afforded no protection in law because they are simply too useful for identifying a particular product range or service, such as "Limousine Hire". Many generic terms may also be descriptive terms. Imagine, if you will, an insurance broker that tried to claim rights for the term 'insurance broker' or the mobile phone manufacturer that attempted to claim the mark 'mobile phone', it is just too silly for words!
It is possible to trademark a distinctive logo that includes these terms. For example, if the individual wanting to use trademark "Limo Sales", produced a unique and distinctive design incorporating those words, it is likely, though never certain, that the mark could be registered. The registration process can be long and quite expensive, whilst you can complete the process yourself, because it is a complex area, there can be some benefit in using specialist solicitors or agents.
The symbol ™ is used to indicate that a word, phrase, logo or design is treated as a trademark by the party. That is, that the party claims rights in the mark, but as alluded to earlier, descriptive and generic terms cannot be trademarked. The symbol ™ is often misused, but this is more likely to be a result of ignorance, rather that any realistic claim to the phrase. Similarly, enforcement of a phrase, simply because it was marked with the symbol ™ would be prone to failure, unless the party could claim some secondary use and have significant resources to employ experts. The trademark must be registered to use the instantly recognisable ® symbol.