How much money would I need to bring with me if I want to enter the United Kingdom from Argentina, is there a minimum for 17 days or will they ask me to show my finances ?
If you are travelling on an Argentina passport, you will be able to apply for leave to enter at a UK port. The applicable rules for this case are found in Immigration Rules for visitors which has this to say about funds...
(the applicant) must have sufficient funds to cover all reasonable costs in relation to their visit without working or accessing public funds. This includes the cost of the return or onward journey, any costs relating to dependants, and the cost of planned activities such as private medical treatment.
So there is no fixed amount of cash specified for a given visit and no specified per diem amount. During the landing interview the Immigration Officer may ask for evidence of financial capacity and they are entitled to refuse entry if they are not satisfied.
In order to help visitors prepare for their landing interview, they publish guidance, which has this to say about financial evidence...
Financial documents showing that you have sufficient funds available. These must clearly show that you have access to the funds, such as:
- bank statements
- building society book
- proof of earnings such as a letter from employer confirming employment details (start date of employment, salary, role, company
- where a third party (who is either in the UK or who will be legally in the UK at the time of your visit) is providing financial support
to you e.g. a business, a friend or a relative, documents to show
they have sufficient resources to support you in addition to
themselves and any dependant family should be provided
Having said all of that, the answers to your questions are...
is there a minimum for 17 days?, no. per the rules there is no minimum amount.
will they ask me to show my finances?, probably yes, especially if it is your first visit or your demographic profile (age, gender, apparent lifestyle, etc) triggers a more intrusive line of questioning. Successful applicants generally bring recent bank statements (3 months) in their name, and their employment contract and an employer's confirmation. If you have a mortgage statement, it can also be helpful.
So much for the rules. You tagged your question with 'budget', which indicates you are also interested in a benchmark to use for planning. You mentioned 'England' and the budget needs for England are wildly divergent depending upon which region you want to visit. Central London/Westminster are the most expensive and it's practical to think in terms of GBP 60 - GBP 125 per day over and above the accommodation (hotel, B&B, social arrangements, etc). However those numbers, or any other concrete numbers, invite debate because they are derived from opinion.
See also: UK immigration check at airport
See also: Refused entry to UK, not sure what to do