I had this reply from my MP this morning.
"Thank you for your email regarding restrictions surrounding the online sale of knifes.
Like you, I, too, am dismayed by rising levels of knife crime. I am similarly shocked by the recent spate of stabbings in London and in other areas across the country that have resulted in the deaths of so many, particularly young, people. I believe we need robust restrictions on the sale of knifes in shops and online in order to help combat knife crime and to prevent underage people or those with nefarious intentions from having access to knifes and blades.
However, I believe you are right that we must be mindful of the unintended consequences of such restrictions and ensure that those who purchase knifes and blades for legitimate reasons, along with legitimate manufactures of said products, are not adversely affected. You highlight some important issues in your email and I have therefore raised your concerns with the Home Secretary, Sajid Javid MP. I will, of course, let you know as soon as I receive a response to my enquiry."