I know less then zero about real estate (and real estate investing) in London unfortunately, but I will say that your planned rent vs property price would fail a common test in the US called the 1% rule. 

I ended up doing some more research yesterday and found the most common strategy would be a sub to followed by a wrap.

These are experienced investors, it is the most common mistake that we make. 

If the seller concessions max out at 3%, the seller can contribute up to 3% of $150,000, or $4,500, to help with closing costs.Here are the seller concession limits for some common loans.Conventional LoansThe limit for conventional loans depends on how much you’re putting down:If your down payment is less than 10%, the seller can contribute up to 3%.If your down payment is between 10% and 25%, the seller can contribute up to 6%.If your down payment is more than 25%, the seller can contribute up to 9%.If you’re buying an investment property, the seller’s contribution is limited to 2%, no matter what your down payment is.FHA LoansFor all FHA loans, the seller can contribute up to 6%.USDA LoansFor USDA loans, the seller can contribute up to 6% of the buyer’s loan amount.

Here, 5% (2.5 each) is very common.

There are two components of management for you to consider: onsite and offsite management.As it relates to onsite management, the common and most generic strategy is to interview the existing tenants to find a capable, trustworthy, willing resident to be your manager.

Is this common practice?

I believe it improves the comfortability of the tenants who lives there.But it has to make Common Sense, Dollars Sense and Business Sense.  

Because I know that this is common in my area for students, are you going to furnish the apt or will your future tenants bring their own furnishings?

She is very rare and she has been integral to the success of Castle Rock as well as those other clients she has cultivated.