I managed to do a good job of my 2 joints and sink and hob cut outs with some experience of a router. Then bashed a finished worktop lifting it into place.
Then made an error cutting the replacement which was a more complicated cut because it was the piece between the two finished bits.
In total this cost me.
Router £160
Jig £40
Cutters £40
Clamps £10
Colorfill £14
G clamps £10? (already owned)
Replace Damaged Worktops £70
Replace Colorfill £14
Transport replacement worktops £40
1 slab of beer after damaging replacement worktop £18
1 Lost morning at work after slab of beer after damaging replacement worktop £50
Time 4 Days (the time soon vanishes due to inexperience and out of square walls
£398 not including last 2 items.
£274 if I had not damage one.
Solution.
Get someone in.
Make clear in advance for that price you want a perfect job with warrantee.
Or.
Fit joining strips yourself.
Not trying to be negative but its a right ball (and head) buster of a job.
PS £300-400 seems a bit steep about 18 months ago a pal of mine in glasgow got someone in to do 2 joints for £120 total for a cracking job.
However someone in the trade here may be able to give you a ball park figure for your area.