Ian, I would suggest that it depends on whether you ever plan to sell the house in the future, or say build an extension, or anything else which would need notification to the lease owner.
Having just sold a leasehold terrace in Crookes, it can be a pain in the backside if the lease owner doesn't play ball.
This again would depend on who would end up as the new lease owner should you not buy it yourself.
I don't think your own legal fees would be excessive, since the lease owner is offering to sell it to you.
In my case, I looked at buying the lease a while ago, as I knew I was going to sell up in 2-3 years time. However, on investigation, I found that my lease owner would be as obstructive as possible regarding the sale.
I could have been looking at many thousands just in my own legal fees, to force the lease sale to me, as the company concerned have something of a reputation of refusing to reply to anything regarding a sale until they receive formal court paperwork. I couldn't even get an accurate estimate of costs, as I'd likely have to employ a barrister as well as a solicitor for the expected court case.
My own sale was delayed, earlier this year, as the lease owner refused to provide any information to prove that I was up to date on my ground rent £3/year.
Jeffrey Shaw of Nether Edge Law is the local expert in Sheffield, which has a rather different arrangement on leases to other parts of the UK; please be careful from whom you accept advice on this forum.
He has a reputation of being a tad abrasive, even to clients, but is apparently the best in the city, specifically for Sheffield leases.
He's also a poster on Sheffield Forum, but doesn't stray into business matters on there.
You could do worse than having a look at this Google review. (not a review of Mr Shaw I should stress) 
PM me with a phone number by all means for further discussion, if you've lost the card I gave you on my visit to collect the blast cabinet, or just give me a bell.
Bill
p.s. the two previous posters got in whilst i was typing a linger reply, but it seems we concur in this case.
Edited By peak4 on 16/10/2019 13:34:22