A farmer in the West of England now holds sheep races on a regular basis, and during the past year over 100 000 people have turned up to watch the proceedings.
Doesn't the time reference in the second half of the sentence (during the past year) take the Past Simple? Shouldn't it be
... 100 000 people turned up to watch ...
Another question, in the sentence
If it weren't for your timely help, Thomas wouldn't have done so well in the test.
isn't the first half of the sentence wrong? Third conditional says it should be
A farmer in the West of England now holds sheep races on a regular basis, and over the past year more than 100 000 people have turned up to watch the proceedings.
What tense is used depends on what is said next:
"...more than 100 000 people have turned up to watch the proceedings. Organisers of this, the final event for the season, are confident of a bumper crop of eager spectators who will have travelled hundreds of miles to be part of this new, seemingly so un-English a sport."
"...more than 100 000 people turned up to watch the proceedings. Other farmers in the district, noting the popularity of the event, are now organising other similar events; so don't be surprised when next you hear about the 200 metre Chicken Scramble and the 75 metre Porky Pig Trotter events in the near future."
You can't learn how tenses are used from single sentences.